I also already have a gamecube and lord knows I've spent enough on this PC already (although I'm thinking about another hard drive right now since I should finally be getting a broadband connex w'in a couple months), but let me suggest, even if it does draw some flames, that you might think outside the box a bit and consider what other things $300 (or in some cases about $500, so save a little more) or so might buy you ....
BTW I have no idea how old you are so I apologize if any of these suggestions might be inappropriate....
--- a decent wristwatch
--- a nice suit (youre gonna need at least one)
--- a very nice pair of brand name dress shoes (use sparingly)
--- a Ruger MkII or 2245 target pistol
--- a quality .38 special/357mag revolver
--- a Rem 870 12 ga. pump shotgun
--- a Glock (ok, you'll need almost $500 for that)
--- 6 more gamecube games!
Sorry if the emphasis on firearms freaks you out. 10 years ago it would have me, but I wish now I had taken some of the money I flat out wasted in my twenties and invested in some basic self-defense hardware. Now that I'm married and have made a (very expensive) kid, it's tough to scrape up that kind of spare cash. Plus, my wife doesn't "like" guns, but if we ever had a burglar she'll be very happy I do have a few of the items I listed above. If you don't have any and you think what I'm saying makes sense, then start out with the 2245 pistol .. it's only .22 caliber and you can practice with it for very cheap. If you think I'm nuts, that's ok too. Just remember there are other things in life that require cash.
Oh and even though I hate M$ I also vote Xbox.:innocent: