I personally wouldn't waste money and get a new setup. Just turn up the aa/af in the game and that should utilize the gpu a good amount, (higher resolution/setting gpu bound; lower resolution cpu bound) but to answer your questions yes it will be a bottleneck but the small hold up wont justify money on a new setup.
Forgive the pm intrusion here, but I couldn't find a relevant current thread with your name in it. Your username was mentioned in another thread regarding dual-rail power supplies and which video cards may or may not work without issues with given amperage ratings. The person naming you seemed to think you had the best information. I have a Thermaltake TR2 500 watt PSU with 12 V DC 1 @ 25 A and 12 V DC 2 @ 18 A. I have done a lot of queries on this on various support forums, but to some extent the advice has been contradictory. There are those, inluding Thermaltake, who say the PSU will not run even an AMD 5750. I have an HTPC and noise is an issue. There are others including AMD and Sapphire who say that this PSU will run the 5750 or even the 5770, although others say the PSU is junk. Would you be kind enough to comment. I will attempt to post this on Tom's Hardware as well.