I just recently sold a 2004 Boxster S for $7500 CAD (about $5650 USD)
It ran great, but had a few relatively minor issues. Needed brake pads, had an oil leak, and low beams werent working on the headlights, roof had to be operated manually. Body was excellent, and the car ran VERY strong!
Had about 150k miles on it, and was an automatic. Below is the listing
2004 Boxster S
Took about a month to sell, and ended up going to a guy about a 20 hour drive away. Lots of tire kickers in the meantime, before sale. Had up to three people contact me a day, with a lot being dreamers and people wanting to trade crap (on a side note.... why does everyone want to trade away their old Harley's ...LOL)
My point is, what OP is asking for is not unreasonable. I am sure their are lots of base boxsters that dont run, that people would be happy to get $4k for.
Anyway, good luck in your search!