You're in a tough position, but unless you are in a position where you are forced into selling, why not keep the Boxster? You have a very nice car that you've put a lot of time and money in to make it unique. I say keep it.
I'm in a fortunate position (no wife, no kids, a great job and no bills), that I have a stable full (9) of Porsches.
And I'm not getting rid of any of them and am looking for my next one!
I have a '99 996 C4 w/ a full Aero kit, 19" GT3 style wheels, sport seats and a whole boat load of factory options. I love it - you'll love the 996 too. Ignore anyone that bad mouths them.
But you really don't have to be Leno to have a Boxster and a 996 in your driveway, so why not have both? Split your driving time between them and you'll keep the miles off, and you'll have 2x as much fun when you take that last look of the day in your drive and see 2 Porsches! Do it!
Rick