Best GPU for Q6700

[Unitologist]

Basically, my current GPU (PNY GeForce 9800 GT EE 512MB) is on it's last leg and I need a replacement. I want the replacement to be a bit of an upgrade as well but I don't want to cause a bottleneck with my CPU (Intel Core 2 Quad Q6700 2.66GHz). So what is the best GPU I can get that will not result in a bottleneck?

I thought I should mention that I do mostly use this PC for gaming. I know it's outdated, but I'm still able to play every game I own. Also, I know I should overclock my CPU but I don't have a motherboard that will allow me to and quite frankly, I'm a bit afraid of screwing things up.

My current PC:
CPU: Intel Core 2 Quad Q6700 2.66GHz
GPU: PNY GeForce 9800 GT EE 512MB
Mobo: Intel DG35EC
RAM: 8GB DDR2 800MHz
PSU: EVGA 500W 80 PLUS
Display: Dell E2011H (1600x900)

Thanks!

 

[clutchc]

Some bottle neck isn't bad. And it won't happen in every game, anyway. Just the games that are heavily CPU dependent and some multiplayer games on a busy 64 player server. The GTX 750 Ti/R7-265 will probably be the best choice to avoid bottle neck. R9-270X/GTX 760 if you don't mind some occasional bottle neck in some games and certain times.