Older Mac Pro issues

I just purchased a new iMac I7 because my 2006 Mac Pro went flaky on me. I want to see if I can save it with a little money. Genius bar at the mall says its the video card. Standard config. on The card is a:
NVIDIA GeForce 7300 GT 256MB (single-link DVI and dual-link DVI) based on looking up ser.#
It says build to order can be:
-ATI Radeon X1900 XT 512MB (two dual-link DVI)
-NVIDIA Quadro FX 4500 512MB (stereo 3D, two dual-link DVI), Two NVIDIA GeForce 7300 GT 256MB
-Three NVIDIA GeForce 7300 GT 256MB
-Four NVIDIA GeForce 7300 GT 256MB
Question is will any other card work other than these? Next question new or used, remember going on what tech says. Dont want to dump a ton of money to find out its just not worth it and I just replaced logic board, RAM etc
thoughts? Thx

You can flash a 4870/5770/5870 (or buy the Apple version), you can use any Fermi card GTX 5XX but will not have a boot screen as long as you are on 10.7.5. If you've done the Chameleon thing to install Mountain Lion you can the flash a 7950/7970 or use them without a out screen. You can use also use Kepler cards GTX6XX..You can aways buy a Mac 7950 or GTX680 if running Mountain Lion

In all of this I'm talking about PC cards.

And look over eBay for a nVidia 8800GT for Mac Pro 1.1. The first release of the card was for model 3.1 but a later decision made it also for the earlier Mac Pro. That may be the cheapest way out. This is the card:-

http://www.ebay.com/itm/1st-Gen-Mac-Pro-nVidia-GeForce-8800GT-512MB-Video-Card-/310260776160