Don't waste your money on alienware go for something like this:
http://www.newegg.com/Product/Produc...82E16883227061
I would suggest going with a dual-core processor, preferably a intel core 2 duo (e8400 is perfect for you) it will outperform the quad core in gaming)
The best advice would actually be to take that money and invest it in a nice mutual fund, or a CD with a good return rate and earn interest on your money, but I am not your parents and can't tell you how to spend your money. Don't waste the money on the PC unless you need it.