Asus M3N78-VM Mother Board.

Any PCI-E graphics card will work in the PCI-E graphics slot.

That's kind of an arbitrary question, but the MB's PCI-E 16x 2.0 capability provides the highest level of video bandwith available. Your system's overall performance capability including CPU rendering ability which is needed to process the video card's functions is certainly something to look at and consider. It's all relavant.

Grekken list you entire system specs., including CPU, RAM, HDs, PSU, etc. and maybe someone can help you find the more powerful video card you want.

I built this board with a PII 940 a couple of months ago. Currently make use of the onboad Radeon 3200 in native Crossfire with an added Radeon 3450. I have an Antec 550w modular PSU, so I have plenty of room if I wanted to add a 4870. a 4870 with the 1GB video RAM would play pretty well on my 40" Samsung 1080P. That card would make good use at higher resolutions. What monitor and PSU do you have. You should be able swap out the Radeon 4870 with the 9800GT with what you have.

http://www.newegg.com/Product/Prod [...] 6813131324

So do you already have the Radeon 4870? Anyway, it is compatible and a stout 500w PSU should power it, if you are not overclocking to extreme 12v power consumption. 8)

Does the Asus M3N78-VM support dual video cards?
haha and could a 500W PS handle two ATI 4970's?

I'm not really good in computer hardware, but in software and such I am...right now I have a nVidia GeForce 9500. Its not the best card, I want a pretty good one that is compatible in the $300 range, with a few gigs of gpu memory

ATI 4xxx series
Nvidia 2XX series.

A lot of great cards are available for under $200 or so.

Native Crossfire will only work with a few cards. Probably the Radeon 2600 and the 3450. I have had my ASUS 780G onboard in Crossfire with a Radeon 3450. It's very weak especially for gaming. Be sure to read your MB manual for the add on cards that will work in Crossfire with your onboard video chip. The Radeon 4890 is under $300. Much of the Nvidia 2xx series also. ATI makes a 4850/4870 X2 also. I currently have a Radeon 3870 in my 780G micro.

If the 9800 supports native crossfire, you may give that a try for now. Then you would have that card available for native crosssfire in the future should you be inclined to use it. I keep my Radeon 3450 for that purpose. I recently bought two Radeon 4850's cheap. I'll use those for a time until new DX11 capable cards show up later this year. Using Windows 7 64 I'll upgrade to a DX 11 card at some point.