No, your CPU will not bottleneck a GTX 295 but your monitor sure will.
Running such a GPU at 1280x1024, or even the 1680x1050 I assume your new monitor to be, will be massive overkill.
Unless you are running at 1920x1200 or higher, you do not need a GTX 295.
A single 4850/4870/GTX 260 is more than powerful enough for your new monitor and a 4670 or 4830 should give you quite a bit of power on your current display.
Unless you are planning on Folding
in your spare cycles, your planned GPU will just be wasting $ and energy.