It's Steam Sale Season!!!

[LeftOfSelf-Centered]

4. I have both Amnesia and the Penumbra series

I already picked up New Vegas during the summer sale, but I have yet to play it (just finished my Fallout 3 replay with all the DLCs, only took me 3 months . I am missing some DLCs though that weren't out yet last summer, which I'm picking up.

I've played Amnesia and it's a great game, I recommend it. Penumbra: Overture I've started, but so far I haven't really gotten into it. I also have Dead Space 2, which I still have to download and play.
I can also recommend the S.T.A.L.K.E.R. games; they're not really horror games per se, but they do have some horror style bits, but they do have some of the best ambiance that I've ever come across in games. Just make sure to set the brightness so that nighttime is realistically dark.

As far as graphics cards are concerned, if you have a desktop, you can probably pick one up that is capable of running the games you mentioned for relatively little money. I don't remember Amnesia being a particular resource hog. My rig is four years old and has an nVidia GeForce 8800GT, and I've yet to come across a game that I have trouble with; I guess that's the lone upside to the consolification of PC gaming, it stopped the hardware arms race.