How about a Karmen Gia? I have no idea about their reliability, power or handling, but one of my friend's had one and it was pretty cool looking. It's been a while, but I think he said he'd bought it for around 3-4 grand, fixed it up, and sold it later for around 10k.
Anyways, you've never really experienced a road-trip until you've done it in a convertible. A trip from the Bay Area down to LA in a rented Mustang convertible convinced one of my friend's to buy a convertible. It's kinda funny. The guy drove around in a beat-up early-90's corolla for the past 10 years. Peeling paint everywhere... his bumper was tied on by rope at one point... But after driving a convertible last fall, he got on the waiting list and picked up a Benz CLK320 this past winter. 🙂
Oh yeah, and another one of my friend's just picked up a new M3 convertible. Man, am I feeling car envy... 🙂