I've done most of the things in this thread by myself, except the traction bar. Haven't gotten around to that yet. Your biggest bang for buck--hands down--will be an intercooler with a AP3 "stage 2" tune of some kind, whether it be a COBB stage 2 OTS map or someone else. I picked mountune and have been very happy with my purchase.
Granted I went really cheap. I picked up a mishimoto J-line intercooler for $140 and spent 12 hours of my own labor fabricating the thing into place. The thing is HUGE. That is one of the cheaper ways to do things. If you don't have 12 hours available, many of the bolt-on intercoolers can be found for about $600. Buying an accessport on top of that puts you right at $1,100.
The second best thing I've done to the car is purchase a set of 15" wheels off of tirerack for about $450 plus $80 a pop per tire. The summer tires in this size are very well priced, and you can keep the wheel diameter the same size, about +/- 2%. Even on summer tires with aggressive, stiff sidewalls the car is extremely comfortable to ride in now. I timed the 5-85 mph and going from 22lb rims to 14lb ones and there is actually a consistent acceleration gain over all the runs I've done. Having trouble figuring out the exact gain, but it is a few tenths less time.