Id suggest to keep your current rig till the new year if you can last that long.
By then we will see a flood of the new G92 from NVIDIA the RV670 from AMD as well as penryns from intel and hopefully new bacy's from AMD
In this time you can save some more money and by a complete rig and use your old as fileserver or something, if thats not your thing you could look at canabilism for your new system (your current HDD, PSU, CASE, SB Audigy, even RAM) and then go for a eBay of your old parts (not that youll get much for em)
It also depends on what settings your happy running crysis at... if you run 1280x1024 with no eye candy than a X1950XT would prolly be a nice upgrade. But i think the whole new system is the best option
I am in the same predicament right now with one of my systems. I am not putting any more money into the old AGP system. I am going to sell it and buy a PCI-E system. So yes, ditch the old system and build new. Take the $230 plus the money from selling the old system (~400?) and start building a new system. An agp system will never run the up and coming new games that require PCI-E and DX10 compatible hardware.
BTW that PSU is overkill for your old system. You could replace it with a 400w psu and use it in the new build.
As for waiting for new technology, I never recommend it. No matter when you buy, there is always something new on the horizon. Unless its being released in the next few days, like the 8800GT, or even a few weeks, then exercise some patience.
go http://www.omegadrivers.net/ let the new drivers drives your card, my self i spare my money on Nvidia GeForce 8800GT / better + the 89$ pentium d, + good gigabyte mb that support 45 nm + nice ddr 2 ram with heatspreader.
Newegg had the GeCube X1950XT back in stock after being out, and I think it'll hold me over until I build an OC'd Q6600/SLI rig this summer. If my system runs well enough, I'll hold off until next year and see how the new intel chips are doing...and hit you guys up for help.