If money right now is tight and you don't play on a high res I'd go for a 9600GT. You can find them at the egg for $70 after rebate:
http://www.newegg.com/Product/Produc...82E16814130393
It would beat both the 85/8600 cards and won't break the bank.
As for ranking the various cards from top to bottom:
88/9800GT
9600GT
6800 Ultra
8600
8500
Flyingbullseye