Jason, sound like you're planning something similar to what I am doing.
So the Cyclone 3000w kit in the US... you have 2 options... http://sickbikeparts.com
I believe both are the same price, but both are slightly different (with regards to what the kit comes with, and what upgrades you can do... as well as just people's preference on which company is better to deal with). First off, check if both have in stock.. I ordered mine a few weeks ago from sickbikeparts... I didn't know they carried it (had been waiting for months for luna to get it in stock) and they came highly recommended by people on the forum. I think Luna might have just finally got theirs back in stock. Second, one important thing worth mentioning (I was actually given the wrong information on this)... Luna's kit comes with the newer/better mounting bracket... The original bracket, what SBPs still has, seems pretty inadequate in person, THO there's like a dozen different mods people have done to improve it. Luna's bracket isn't incredible, but definitely better, and you MIGHT be able to make due without any mods. BUT, if you are like me, and got it from SBPs, you can actually order the bracket directly from cyclone in taiwan (http://www.cyclone-e-bikes.com
)... I just did yesterday. It's $35 and shipping originally showed up as $35 (so $70 total) but when I went to pay, suddenly it went up to ~$53 shipping. I emailed to complain/ask for other options (at 4am PST Sunday morning, nto expecting a response for days)... got a response 1 minute later... told me to order, and they would refund me $20 (which they did immediately.. AND they have already shipped it and given me a EMS tracking number, so should be here SOO much faster than I had expected). SBP's kit comes with a chain, and I think there may be one or two other small differences... and each site's upgrade options are way different. Luna makes it easier to upgrade (BUT, if you email SBPs, they will tell you to order the 'upgrades' you want, comment in you order, and they will refund you some money). I had my eyes on the Luna tic crankset/freewheel upgrade... but got SBPs Ultra HD Freewheel upgrade (made by white industries... so definitely quality.. but very pricey for a freewheel.. BUT I am a big fan of white industries).
Now, with that all said, and if both have it in stock.. you'd probably be leaning towards Luna (again, this is partially dependent on what upgrades you want... tho most importantly, whether you want to build your own mount/enhancements, or have to order one from Taiwan, vs getting the better one in the kit. BUT, there is more to the story... while Luna definitely seems like a legit reputable company (I have no reason to think differently, others may argue)... SBPs totally wins on customer service. For me Luna took days to answer every email, and rarely answered all my questions... with SBPs, I emailed them in the morning, got a ful response within an hour... and through that day had something like a 15 email conversation ending with me ordering from them. I've also heard multiple people say that if they were to have issues with the kit/motor... they would feel much safer dealing with SBPs (again, I personally have nothing bad to say about Luna.. BUT I can say I think SBPs is wayy more responsive and much easier to get a hold of... Luna seems a little stretched too thin). I personally do not regret at all ordering from SBPs, and would do so again... THO... it would be a tough decision, Luna definitely has it's benefits (I wish SBPs would just get the upgraded mount, then it would be much easier... but considering how quick cyclone's service ended up being... not a big deal to me right now).
Second, if you want a 72v battery... I believe that's generally considered a 20s, not 19s (given at full charge a 20s is higher than 72v... BUT 20s is the highest supported by the stock controller... it;s what I'm going with.. and I am also building my own pack).
For me, I wanted a pack that would hit the 3000w mark, BUT it needs to be as light as possible (I don't have an elevator in my building, and need to carry the bike up/down a flight of stairs to use each time).... and 95% of my rides on this will be in the 1-4 mile range, so I don't need high capacity normally. I ended up findidng the Sanyo 20700A battery... a 30A 3,1000mAh per a cell (YES 30AMP continuous per cell)... meanging, instead of needing 80-100+ batteries to hit the 3000w mark... I can do it with 40. On top of that, you can get these batteries from brand new Bosch 18v 6.3ah battery packs (10 per a pack... and can get 2 packs for $105 shipped on ebay brand new http://r.ebay.com/DSNQ84
)... AND to top it off.. for my 20s2p pack, it's literally exactly 4 bosch 18v 6.3ah battery packs in series.... SO i can make use of their current structure, with their 'coolpack 2.0' battery holder technology, and their laser welded copper plates... a win, win, win for me. And I plan on eeither have 2-3 of these packs (so I have an option for longer rides) or I might just make a second pack twice the size, a 20s4p. Either way.. these batteries are from a top brand... very high quality.. the new 20700 form factor... and at an incredible price (comes to $5.25 a battery).... plus I get the bonuses I just described on top of the batteries. On top of all that, these are pretty new battery packs from Bosch... so buying them off ebay at an incredible price does not mean I am getting old/defunct battery packs.. they are all pretty much brand new. I can't recommend them more.
As for ebrake cutoff... others may say different.. but I don;t think it's that necessary. Given, I did get them... but only because I found a set brand new on ebay for half price. THO, it seems a lot of people don't like the stock ones, finding them hard to install (I know grin, the makers of the cycle analyst, has a new design that seems much better, but cost a little more, nothing crazy)
As for the cycle analyst.. do you need one, probably not... But again, I absolutely bought one... did not hesitate or have to think about it. It's not too expensive, and has TON of benefits to it.... too many to list... some major, some small.. but both major and small ones can be really nice. But, you can always get one later if you don't get one now.... but I feel like it's almost a must have based on how useful they are.
Anyway, hope that answers your questions... and good luck... should be a fun bike when you are done.