Too easy. Go from 18s on your battery to 24s and 30-35A on the controller. Check with Ypedal regarding the safe max current for a 407. Maybe with your light load and flat terrain it's no problem going to 40A. Include a programmable controller in the mix for future flexibility, and eek out a bit more top end with the 110 or 120% max limit on the speed limit settings. You could go even further on the acceleration part with even more current if you learn the limits of your motor, so you know intuitively when you've ridden it hard, and ease on and off the throttle a bit shortly afterward.
Also, those X series motors have a cooling advantage over other motors if you go ventilated. That's because the overlapping winding strategy that creates the low cogging torque for pedal only results in a lot of extra copper on the end windings, so the cooling air flow comes in contact much more copper than all of the other more common type motors. Justin's testing showed that there's really no way to keep water out of the motor if you ride in the rain, so there's really no reason not to ventilate, and it might even enable you to go to 50A or higher, which at your weight should be high in fun quotient.
In doing so, please use a well thought out ventilation approach, and no just swiss cheese the side covers. The air inside our hubbies spins due to the side covers. This spinning creates a centrifugal force pushing the air to the perimeter, so intake should be as near the axle as practical and exhaust as close to the perimeter as possible. The splayed stator laminations of the X series motors creates an angled channel at each tooth that stimulated some air flow through the magnetic gap naturally. On my X4 motor that flow is from the right to the left side, so I believe the best passive ventilation strategy for that motor is to intake air near the axle only on the right side with exhaust holes at the perimeter of both covers. Smaller holes permits you to get closer to the lip on each cover that locks the magnet backing ring in place, and angling the holes so the air exits rearward at the top of the rotation (the creates a left and right cover so be careful of correct orientation) stimulates a freer flow. This is all much easier than my usual detailed explanation makes it sound, and only very basic tools are needed, a center punch to mark nice evenly spaced places to drill so the drill bit doesn't "walk" on that curved surface, a hammer, a drill, a 1/4" or 5/16" drill bit, and a marker.
Be sure to replace those bearings while you're doing the upgrade to make your motor good for many more trouble free years.
Also, spend some time and a few bucks addressing aerodynamics. The cycling calculator here http://www.kreuzotter.de/english/espeed.htm
shows the power requirement increases by over 1000 watts going up from 30mph to 40mph. Since you're looking at about 2kw, small differences pay huge dividends. eg at 40mph on a racing bike simply going from hands on the tops to hands on the drops saves 500W. Even just the type of tire can save 100W or more.
If you're itching for a new rig and get new everything so you can just power through it, I completely understand, though I would suggest modifying your target to 50-55mph as an absolute top speed in a tucked position. That's even if you never intend on going that fast. That will give you nice zippy acceleration in the 30-40mph range where you need it the most to mix safely with traffic. If your bike tops out at 40 on the flats, then accelerating from 35 up to 40 will suck. Also, any slight incline or headwind will force you below 40. My main bike will go 60 but I've only done it twice just to see. Typically I ride between 30 and 40 mph, and sometimes 45 or 50 on some good roads that warrant it. That puts my peak power rpm around 30ish, so when I get behind some idiot driving too slow, I just zip right past. Just like I'd never own a car that I needed to drive around at WOT, I wouldn't own an ebike that needed WOT either.
That said, if you're looking for much better performance with a cheap price tag, some extra batts in series and a new controller is a cheap way to get there. Then if you still have some extra dough, spend it on more batts, not for more range (though riding conservatively you'd have more range), but to get the same range but quicker and a whole lot more fun. EBikes at 20A are for old people and children.
Sorry for the long-winded post with no pics or videos, but at least it's solid info.