That 7500 you linked too has even less support than the Matrox you linked to. ATI dropped support for it back before Vista came out, so at best you would have to use the ;ast XP driver for it (and then no Aero, and not sure what if any affect those old drivers would have on the Nvidia drivers).
One reason for recommending the 6200 is to avoid any possible driver problems. Both cards use the WDDM 1.0 driver model, Windows Display Driver Model - Wikipedia, the free encyclopedia
where that old 7500 would be stuck using the XPDM, There are slightly newer Nvidia PCI cards (8400 GS for example), but they use the WDDM 1.1 driver model. Now as far as I know you can have cards that use different driver models, but they cannot use the same manufacturer driver (Nvidia WDDm 1.0 with a card that uses WDDM 1.1). What happens is that the older spec driver cancels out the newer one, causing the newer card to not work (quite a few threads about it here in the forum). That's why I said as far as I know you can mix them as long as they are from different manufacturers (ATI with Nvidia, Nvidia with ATI), but I don't recall seeing confirmation one way or the other.
Speaking of drivers from that Speccy screen shot you haven't installed either the audio or video drivers, both are running on the Windows default drivers. For the video considering the age of the 7600 GS I would avoid the latest drivers (2xx.xx series) and go with an older driver, something like this one, NVIDIA DRIVERS 197.45 WHQL
for the audio according to the specs for the motherboard it has the Realtek ALC882, which can find download links too here, Latest Realtek HD Audio Driver Version
As for that 1080p issue you mentioned, let's get the drivers installed and then see how that goes.
Really? without needing to SLI both cards?
SLI has never been needed to use two Nvidia cards for more than 2 monitors. In fact when Nvidia's version of SLI came out (3dfx was first) if you were running two cards in SLI and more than 2 monitors, you had to disable SLI for the extras to work.