I have a pretty humble system. Humble yet effective.
Custom PC (Big massive black box. Dont remember the name. Size matters. 6 fans)
Intel Core2Duo (no overclocking)
4 gig of ram (3.2 cuz fkn 32bit xp is lame)
Nvidia 260 GTX
I have 2 TB HD's but only use 1 so far.
I have all this hooked to my 52 inch HD LCD TV. Surround sound n chit.
Media center PC basically. Just got sick of having a "Computer Area". With today's technology there really no reason for it. Hook the PC to ur TV and have it all in one area. You'll enjoy it more im certain.
I paid for all this. Really didnt cost much at all(except the TV of course

)
There was a hell of a deal on all the parts I purchased for the PC and I got the surround system at the pawn shop for cheap.
The greatest thing is... It runs almost everything at 90-100 percent and seems VERY compatible. Just luck I think. I never ran into any problems with SMB like others did (Except the alt tab stuff)
PS. Since you mentioned Portal.. Are you as psyched as me about the soon to be released Portal 2 ?

It will be the only game released in the last 2 years that I MAY consider better than Super Meat Boy. I may take the day off work when it is released LOL .