"Best" Gaming system

The poll i had running shows me that Windows is still strong in gaming. I havent really run a windows maching in over 10 years now; so I was wondering what people suggest would be a good system to get back into the machine, especially (basically only) for gaming. I miss playing games on my machine, and Steam for mac has good games, but the best ones still are Windows Only.

I'm looking for advice on a well rounded portable system that will be good for gaming. I would like, but cant afford, an ultimate system; so something in the middle that is a good value would help me a lot.

What do you guys thing would be good?