Upgrading system: CPU vs GPU

I desperately need to upgrade my current system (HP XW8400) and I have to do this piecemeal. The system is a dual Xeon 3.0Ghz with 16Gb and a Quadro FX3800. The question is if I replace the video card for something a bit more current (and faster) will I see any real improvement with Resolve Lite, or will the CPUs hold up the system past the point of making a video card upgrade useful?

Please, no Upgrade everything comments. I already know that. But until the job market turns around for me, that's not a real option (everything works, it's just slow).

GPU first (with max GPU memory) then CPU....

Thanks for the advice. It was most excellent. I replaced the old Quadro with a GT 760 and the difference is remarkable. I hadn't realized just how GPU centric Resolve really was. The rendering rates for a basic color correction (1 node) went from 1.5 FPS to 18.5 FPS. So my 2 hour video now renders in just over 3 hours and not the 32 hours it took previously.

Excellent!

Yes, resolve is really GPU hungry.....