I Need Video Card Advice

[theRepublic]

theRepublic said:

vlad321 said:
Good news is that you have 1 PICe 16x available. The bad news is that I have no idea if Pentium 4 and 1 gig are able to support Portal and LoL. On the other hand, if those are enough, then you can just buy a card for sub 100 to play those two specific games and you'd be good. The bad news to that is that you might need a better power supply, since the specs dont say what it is you have we can't say if it will be enough or not.

This http://support.gateway.com/s/PC/R/5022/5022cl2.shtml seems to insinuate it is 300 W.  I will open up the case and check later though.

I upgraded to 4 GB of memory.  I'm not sure how good "Can you run it" is, but ii says that I meet all the recomended specs except for the video card.  The video card fails miserably of course.

It is 300 W.  Any good way to know if the system will be able to handle a video card?