Best video card for an older system?

That plain 650 is not a huge leap over a 8800GT 1gig card.

GeForce 8800 GT 1GB vs GeForce GTX 650 – Performance Comparison Benchmarks @ Hardware Compare

You want to jump a tier out of the 128-bit memory architecture.

Nvidia is priced out, I'd go with:

MSI R7850 Twin Frozr 2GD5/OC Radeon HD 7850 2GB 256-bit GDDR5 PCI Express 3.0 x16 HDCP Ready CrossFireX Support Video Card - Newegg.com

Comes with Crysis 3 free offer!

GeForce 8800 GT 1GB vs Radeon HD 7850 – Performance Comparison Benchmarks @ Hardware Compare

GeForce GTX 650 vs Radeon HD 7850 – Performance Comparison Benchmarks @ Hardware Compare

See? :) You have a 650W PSU, that should be plenty for the upgrade.

Only possible problem, these cards are big, you might have to check your case, I have the big brother to that card, it looks identical.

My last 3 cards have all been huge, 8800 GTS, and a 5850 being the other 2, this is my case, and I have maybe an extra inch or those cards wouldn't have made it:

http://www.hardwaresecrets.com/article/999

Nah get the 7850, if you wind up upgrading to newer mobo and CPU later, that card will still be decent, even if your performance is limited SOME, better video is not a bad thing.

It's a good price point too, I spent $400 on mine, at the time I think the 7850 was still $250ish.

Video card is the one part I have system hopped more than once.

Looking at specs, I forgot to mention need for PCIe 16x v2.0 slot for compatibility, looking at specs of your motherboard, didn't say what revision, that could be a problem if it's 1.x and the card doesn't support 1.x, not a definite or anything.

I would go here and confirm that, when they are open:

http://www.service.asus.com/#!consumer/csn9
^if in USA or Canada.

I tried to, unfortunately now closed.

Found a thread where someone put in a 7750 and said it worked great, so it's probably a non-issue.

Apparently, that mobo can handle the Phenom II x4 945 CPU with the right revision/bios update, also.