Actually, the damage wasn't because they were ebay fans.
Most fans come with a warning to only connect fans to the other end of their molex connectors as the wire can't handle the current a 3870x2 would draw.
If these fans didn't warn you of that, maybe you've got a case for a dispute but if they did I'd say you're out of luck.
I'm not saying that it's your fault because you didn't know and can't be expected to do everything right on the first go round.
It's a crappy way to learn but unfortunately I doubt it's a fault of the fans' manufacturer that it can't supply 15+ Amps of current, very few computer parts actually need that much current and they all usually have a dedicated connector from the PSU.
You might be better off replacing the PSU as well, it could be okay but if it wasn't you'd find out and it wouldn't be fun, it sucks to have this happen but I've had plenty of hardware die on me and the best thing to do is to buy a replacement and learn from it.
im going to have to save for a long time now to replace my card took 4 months to save for my 3870x2 i have only had it for a couple of months