The easiest way to tell if you are limited by CPU or GPU is to test at different resolutions.
With non-CPU intensive applications the framerates will start ridiculously high but usually drop by the higher resolutions. If the framerates start out low and don't change no matter what resolution then that test (or game) is CPU limited.
For example with Q3 you might see 300 fps @640x480, 1024x768. Framerates might start to drop off at 1280x1024, say 220 fps, and then at 1600x1200 you might see only 100 fps (all just example numbers).
Take UT2004 on the same system. You might hit a framerate limit of only 40 fps (another example only) but it's the same at all resolutions. Doesn't matter high or low. This is being CPU limited.
Now in the latter example even though the CPU is limiting framerates this is not a constant number. The upper limit will change with a faster card. Performance will still be CPU bound (assuming the same system) but the ceiling will be raised. Perhaps instead of that 40 fps ceiling you now have 60 fps.
Over-simpified, there are always two components to graphics performance, CPU calculations and GPU rendering. Speed up one component or the other and you always get some benefit.
In your case, with a newer card I think you will get some framerate increases. At least at higher resolutions I think you will. You should get some new eye candy, plus be able to run AA at higher resolutions than you could before, and even run AA in some games in which performance was to slow to run AA at all.
How much gain you get I couldn't say but I think I can tell you a way to kind of guage what you might get.
In the old UT2003 (that's '03 not '04) you can edit the UT2003.INI file and select the NULL renderer (vs the D3D renderer). This completely takes the video card out of the equation. Benchmarking in this mode will tell you the absolute upper limit of framerates on you system (UT2003 only, of course). You need to use the UT2003 benchmark since there is no actual video going on to use with FRAPS. You can compare these "ideal" results with what you are actually see with your TI4400. The difference is the room for improvement.
Obviously you can't obtain the ideal (becausing rendering always takes SOME time) but the faster the video card the closer you get to the ideal. The numbers will give you an idea of what your current system is capable of and where you currently stand. Plus you can use those ideal numbers to compare with the actual numbers of better systems.
I wish more games had this kind of benchmarking.
<b>56K, slow and steady does not win the race on internet!</b><P ID="edit"><FONT SIZE=-1><EM>Edited by phsstpok on 04/20/04 10:45 AM.</EM></FONT></P>