I would recommend exactly what Chalex suggests. I can't fault it at all, might be a good idea to grab another 2GB of memory though at that price.

I myself wouldn't recommend an AMD processor, simply because I haven't heard from anyone who has on and I don't know how they perform compared to intel. I would play safe and get an intel.

Stay away from the 9800GT, AFAIK, it's just a rebranded 8800GT with the 9 at the front to make people think it's new and better. A 4850 is a much much better choice at the same price. If you are gaming below 1920x1200 (22" and lower) it's the perfect card. If you're planning to get a 24", i'd try to stretch for a 4870.