Proportional PAS for cheap hub motor

So 4 or 5 months ago I bought one of those cheap 1000W hub motor kits on the 'Bay http://www.ebay.com/itm/48V-Front-Wheel-Electric-Bicycle-Motor-Conversion-Kit-1000W-E-Bike-Cycling-Hub-/221691273393?hash=item339dd460b1:g:OakAAOSw3YNXa5n~ for my bike, and also a BBSHD for my wife's bike. Needless to say I now have a bit of ebike-envy. The part I like the best about her setup is the ability to set PAS level as well as the PAS being proportional on her bike, where as on my bike when I turn the pedals it just goes straight to 11. Her battery lasts a lot longer than mine as a result.

So I'd like to upgrade my controller to something that would still be compatible with my hub motor, but have proportional PAS and have adjustable PAS levels. Does anyone have a suggestion? I'd like to keep the upgrade below $400.