There is no way I would suggest buying a new car in your situation. I'd go a couple years old, at least. You could do as Steve mentioned, which is good advice. But I would NOT pay the premium for low miles, in fact, I'd buy one with higher miles. All cars need the same basic things at about 40K (tires, brakes, tune) so why not buy one with those things just done and be good for another 40? Or one where it was just done for the second time at 80?
The supply of four year old Porsches is also greater. They're just getting off lease, and they're just getting out of warranty. Cheapest purchase point?
If it's a Porsche, then the hit for miles is a STEEP curve. The spread between one with 10K and 80K can be $10000 plus on a 4 year old car. I can fix a lot for $10K, or better yet, buy one hell of an extended warranty and have $$ for repairs. The irony is that a 4 yr old Porsche with 10K may still need some of the same work because it has sat so much. It's already been done on the other car, and gets its excercise. 911's commonly go 200K and people are still willing to buy them (for quite a bit IMO).
So buy your Boxster S as a 2001/2002 with 50-80K and look for a good pedigree. You should be able to pick one up for about $25K
like this one on eBay . A 2001 911 Coupe runs only $10K more. Three years from now with 150K, it will still be worth decent money.
Just another take.
E