Can i run pc power supplies in tandem

If done correctly, shouldn't be a problem , but a single higher wattage unit is a better option.

I need a video card and that requires more power. I have a very limited budget.

Its a risky endeavour, but if you hook up the cable properly, shouldn't be a problem. However, like my fellow replier said, I single higher wattage PSU would be better, wouldn't cost as much in money/electric bill terms.

What video card were you thinking about ?

I think I will skip the tandom power supply and find one higher power unit.
I am looking at the Radeon HD4770 because of some reviews I have read about it. I would love to get a higher power card but I don't have extra cash to spend on it.

perhaps this article will help

Here's the "winners" from THG's latest (December) GFX Roundup
Best Graphics Cards For The Money: December '09

$50 - HD 4650
$65 - HD 4670 / 9600 GSO
$85 - 9600 GT
$95 - 9600 GT / HD 4830
$110 - GTS 250 512 MB
$120 - GTS 250 1 GB
$155 - HD 5770 / GTX 260
$200 - HD 4890
$240 - 2 x GTS 250
$310 - No winner (HD 5850 Honorable Mention)
$330 - 2 x GTX 260 / 2 x HD 5770
$400 - 2 x HD 4890
$410 - No winner (HD 5870 Honorable Mention)
$465 - No winner (GTX 295 Honorable Mention)
$625 - No winner (HD 5970 Honorable Mention)http://www.tomshardware.com/reviews/geforce-310-5970,24...

Are the hd 4650 and 4670 able to run semi modern games? ie.. Batman Arkham Asylum, combat flight simulators etc

Batman, in all it's glory, requires a PhysX card which is nVidia's territory. Read about the requirements here:

http://www.tomshardware.com/reviews/batman-arkham-asylu...

And that's where things get expensive. A single GeForce 9600 GT isn't going to cut it if you want a 30 FPS minimum frame rate. You'll need a GeForce GTS 250 to play at 1680x1050 with normal PhysX enabled, and a GeForce GTX 260 can just handle 1920x1200. With PhysX set to High, even the GeForce GTX 260 can't handle a minimum frame rate of 30 FPS at 1280x1024, so you should consider a dedicated PhysX card if you want high resolution play (and you have a free PCI Express slot available on your motherboard).

The good news here is that a GeForce GT 220 can be had for as little as $65 online, and as a dedicated PhysX card, it will guarantee that the High PhysX setting won't bottleneck performance. Even at 1920x1200, the GT 220 produced a minimum frame rate of 36 FPS as a dedicated PhysX card. Using more expensive solutions as dedicated PhysX processors didn't produce appreciably higher frame rates, so the GeForce GT 220 is a real PhysX champion for the price.

Decide whether PhysX is worth it here:

http://www.firingsquad.com/hardware/batman_arkham_asylu...

So, it looks like a 260 + a 220 or about $250 at 1920 x 1200 for Batman.

If you want ATI as your main GFX, the 220 could still work as dedicated PhysX card, but you'd need to dp a drive rhack and have windows 7.

http://www.tomshardware.com/news/nvidia-ATI-physx-patch...

Ouch.
What happens if I run a lesser nvidia card and a 220?
And am I donig this only for the Batman game? Or will it benefit all future games?
Obviously I will have to upgrade power supply.

Do I need to disable the graphics chip when I install a card?

lol u have to disable the integrated graphics but it should do that by itself...