I recently moved to pc and next-gen consoles are coming out. Since they have a monthly subscription for online gaming. Pc is the only way to go. I am looking for a sub $600 gaming pc. And I am ONLY GAMING.
If you're building a PC, there are many, many different ways to go. If you're planning to buy a PC (it kind of sounded like what you were asking about) I recommend taking a look at this: http://www.digitalstormonline.com/vanquish.asp
It should get you through several years of gaming at above-console levels, while staying as close to your budget as possible.