I'm in the process of building a new computer but I figured that I could order a GPU+PSU and use it now rather than sit on a nest egg and ordering everything at once. I'm not sure if it's even worth the time though considering I have a fairly old CPU and I'm not quite sure if it'll bottleneck the 7950 to the point that it's hardly worth upgrading from my 7750 atm. Would it be viable to order my GPU and PSU now or just wait?
Since you are intending on continuing your upgrade as funds become available, by all means go for the HD 7950 now if you have the money. Sure, the 2.5GHZ C2Q will hold it back some, but it will be a major improvement in gaming over the HD 7750.
yes, severely. however, if you could overclock the cpu to 3ghz or so, that might buy you some time while you get some funds together for a full upgrade. you will notice increased performance from a 7950 at 1080p over your 7750, but you wont be using it to its full potential. IF your going to get a new cpu/motherboard in the near future then its not really an issue. It might actually be preferable to wait on the cpu upgrade anyway unless you have an urgent need for it, as new sockets are coming out from intel in the very near future, and amd will also be changing sockets soon enough. So if you bought a tip end cpu and motherboard now from either manufacturer, you would be stuck with that with no upgrade path. Although a top end i5/i7/8350 cpu should last you around 4 years.