I would recommend building one yourself. It's a lot easier than you think, and we'll be happy to help out if you have any problems, here is a good guide to get you started: http://www.buildyourown.org.uk/
You can get a lot more for your money and it'll be
This the site to buy your parts off: http://www.newegg.com/
And what online gaming will you be doing? MMOs?, or COD4/C:SS etc?
You won't have to spend that much if you decide to do it yourself though. 1K max will be plenty.
Please answer these questions and then we can help you with your parts selection.