Well, generally the 8800GT's ran and still run pretty hot, and also don't cool well. Also, I wouldn't buy used cards, because you don't know what they've been through in terms of temperature and abuse. You can't get a video card carfax.......videocardfax
The 8800GT though if they fully worked and were well taken care of, would be good performers.
The 560Ti is surely more expensive than the 8800GTs, yet would be cooler, use less power, and perform better.
What I would get? Neither. I would go for the 7850, as its the same price as the 560Ti and is quicker, while it also uses less power.