My comments (Note: I have a 911, not a Boxster):
1. Bixenons: a must.
2. Sport seats: I have spot seats on my 997 and had standard seats on my 996. The standard seats are excellent and the sport seats are really no better. A matter of personal comfort. I will not get sport seats again.
3. PASM: I definitely would NOT get PASM. It does not shave seconds off of lap times. Most people get better lap times with PASM in normal mode than sport mode. PASM limits your choices of aftermarket suspension modifications. I believe that only Bilstein is properly compatible with PASM, and there are plenty of cases of prematuer shock failure with other lowering springs. The standard suspension (on a 911 at least) is very good, and you can easily modify it if you don't like it. IMO, PASM is a gimmick.
4. Heated seats: a must for a convertible.
5. Sport chrono: you hadn't mentioned this but I thought I'd chime in on it anyways. TOTAL waste of money. The wart is f'ugly, and the stopwatch fxn is useless on the track (if you are driving well, there's no way to coordinate using it accurately). With manual transmission, my opinion is that the different throttle maps are a pain, especially if you like to throttle blip on downshifts, because the amount of throttle you get for any given pedal position changes, so you end up picking one for consistency anyways. It might make more sense for a tiptronic.
6. BOSE: I would definitely get the upgraded stereo, especially in a convertible. Its still not that great, but its much better than the standard unit.
7. 18 vs 19 inch wheels: an aesthetic preference.
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"Rational arguments don't work on religious people, otherwise there'd be no religious people."-House