Of the choices listed by the OP, I find the 993 the most appealing. Maybe check out Excellence Magazine for their used car valuations. This might be a car that could gain some value in the years to come, helping to offset the maintenance costs.
I'd also consider a Z4 Coupe. Here's an M with high miles, but it's within the price range:
http://sfbay.craigslist.org/eby/ctd/1448792246.html