i was just wondering how much do u guys think a AMD Athlon 64 X2 5000+ Brisbane 2.6GHz 2 x 512KB L2 Cache Socket AM2 65W Dual-Core Black Edition Processor would
bottleneck a 4850?

Depends on the game, but I will tell you that I upgraded from a S939 X2 3800+ @2.5GHz to a Core 2 Duo E6750 @3.2GHz and I couldn't tell much of a difference in Crysis. UE3 games are supposedly more CPU bound but I suspect that your Brisbane will be good enough for any UE3 game currently on the market.

bottlenecking is an evil word used by people who don't know what they are talking about. very rarely is a cpu responsible for unplayable minimum fps which is the best definition of a bottleneck i have been able to come up with. their is no such thing as a balanced system.

I don't think it will be a bottleneck at all, especially if you play at something like 1680x1050 and enable lots of eye candy. That X2 5000+ is still a very good CPU.