Mid-range newer video cards will be 2.0, 2.1 or 3.0.
I've run my pci-e v2.0 video cards in both of my pci-e 1.x systems with excellent results.
My video benchmark scores are within 5 - 10% of newer quad core systems running with similar GTX 460 higher end cards.
From what I've seen in the ASRock forum, there are many video card issues where the motherboard does not recognize video cards.
These issues include many motherboard models, where the solution is sometimes related to bios versions.
Check out web reviews of your motherboard and see which video cards they used when evaluating the system.
You will need to contact tech support at ASRock > Support Request Form to get definitive answers.
Make sure that your power supply is a high quality unit that can easily power your video card.
Many cheapy power supplies don't put out anywhere near their "rated" power output.