There are so many of these around, IMHO I see no reason to pay a premium for a '97, which as others have mentioned has all the short comings and none of the updates. And $11k is too much.
It's a Boxster; it will never be collectable, so low miles don't really count for much. Maintenance will cost the same no matter the miles.
The dealer wanting $20k for an '04S is dreaming!
Offer these guys $7.5k and keep the rest for maint and upgrades! (after a PPI!)
Cars for Sale: 1997 Porsche Boxster in Carrollton, TX 75006: Convertible Details - 317563995 - AutoTrader.com