Need Advice for Computer Upgrade

[ramuji]

Slimebeast said:

 Wth is "low profile"?

I've always been told from reviews that only 2 factors are relevant:

1. If card is single slot or double slot (very few are double slot)
2. length of the card

 

 

This is one place I've been reading about half-length and half-height ("low-profile") cards: http://en.wikipedia.org/wiki/Peripheral_Component_Interconnect#Physical_card_dimensions

Even if I am able to find a decent "low-profile" card, it seems I'm going to also need to upgrade my power supply. And there may be some other additions required that I'm not yet aware of.
The whole point of me considering this upgrade is to weigh my options versus simply buying an Xbox360, for example. 
As I said in my OP, I originally bought this computer for work only, without gaming in mind, so I may have limited myself hadware-wise from the very beginning.