Need some direction on buying a new video card.

Hello, I've been away from PC hardware for far too long and I don't know what's what anymore in the world of video cards. I have a general idea of what I want and what I need. Hoping you guys could direct me further with the knowledge you have.

That out of the way, I'm looking for a reliable budget card that runs "relatively" cool and is "relatively" power efficient to replace my onboard geforce 7100.

The card must be PCIe 1.0a compliant(I've heard this limits my options) and have enough oomf to run a game like Mass Effect at lower resolutions(1280x800 etc. or lower) fairly smooth. The Mass Effect requirements are here and lists the GeForce 7900 GTX and ATI X1800 XL or higher as recommended options. It's the only piece of software I have to guage performance atm, so I hope it's adequate. As it is, my onboard video can't even run 640x480 at decent frame rates after turning everything off.

The PC is pretty basic. I'm using a fully integrated motherboard plus hard drive and dvd-rom and that's it(nforce 630i/e5300/2gb ddr2-6400). My power supply is an antec neo-HE 380w. So I going to wager I have *some* power to spare for discreet graphics.

I'd like to get one of the newer geforce or radeon models, but I'm not sure how my older PCIe bus will limit me there. Mainly I just want a reliable card that's cool and efficient and has the guts to run my favorite games reasonably well.