X1800 GTO2 upgrading to GeForce 8800 GT is it worth it?

I have a Sapphire Radeon X1800GTO2 Limited edition 512MB GDDR3 Memory, Dual DVI, VIVO, Cross fire edition graphics card. - - - and I haven't gamed in ages (though thinking of maybe getting back into it again)

[running on:-
AMD Phenom Quad Core 9850 Black edition
Gigabyte GA-MA790X-DS4 motherboard
2x 2GB PC8500 DDR3 at 1066Mhz memory
IDE Seagate barracuda 7200rpm 8mb cach 160GB hard drive]

would there be a major graphic improvement to upgrade to a GeForce 8800 GT 512Mb DDR3 card? or GeForce 9800 GT 512Mb DDR3 card? - - - - basically will it be worth the upgrade??

Second question:
I orginally used my graphics card with an analogue adatpter on an old fashioned monitor. I have just purchased a Samsung 22" Wide TFT LCD 225BW monitor (in analogue its worse than my old monitor, picture quality is sh*t) But the connectors on the graphics card do not match the connectors for the DVI cable that came with the monitor? What kind of connector adapter do I need to run this via its DVI mode??

If you are planning on gaming again it will be a worthwhile upgrade. Btw 9800gt = 8800gt, same chip, everything

i dont think its worth it, maybe a faster card but not 8800gt