1) get the big wheels, they are expensive to buy afterwards. My Carrera 5 spokes with the Boxster fit were nearly $500 a piece. Add another $1000 for the right tires (the most important mod).
2)If you are into playing your stereo with the top down the wind deflector is a must have. The sound system in my car (6 OEM speakers and 4 chanell amp) is the best top down STOCK experience I've ever experienced in any car (by a mile)
3) I have GT3 Seats your wife will LOVE those much better
4)its very cool.
5) If buying used get an S, get at least a 2000, and try and get as many options as possible because they are very expensive to get afterwards. With other cars I think its the other way around. Low mileage is crucial.
If buying new I would encourage you to buy used. A 2nd hand Boxster is the best deal in sportscars.