It's great to hear more people are getting sponsored to game, and if you're good enough to get a sponsor, my hat's off to you. Asking for help is good, but know you're opening yourself up to get flamed by people for a variety of reasons.
Saying that, it's not important what other people think, however, you should know what you're driving well enough to be able to get the results you're after. Graphics, motherboard, processor; they all play a vital role in maximizing the results you're after, and although you don't need to be a technician, you should have a good understanding of the parts you're going to need to get the best results.
As a gamer, I'd recommend AMD and nVidia, as they're tuned more to gamers than anything. Use high performance ram from a company such as OZC or Mushkin, your hard drives should be 10,000 RPM drives, as being able to access information faster helps reduce latency. As good as CRT monitors go, using an LCD with a great refresh rate will benefit the mobility of your system. If you're going to be moving your system a lot, get yourself a set of Xbags (
www.xbags.com) to carry your system in. I have yet to find anything like them, and for those that are interested in case carryiers, we will be doing a review on the Xbags line of PC carriers in the near future.
Power is the other concern you should have. The stability of your system is primarily based on how dependable and stable your supply of power is. There are many companies that sell PSU's, but only a few of them have dependable power supplies.
One other note. The professional gamers I know, don't use large resolutions with high detailing, they use 800x600 with mid to low detail to maintain high frame rates in games with lots of things going on on screen. It's those of us who play in our homes and offices that go for the highest detailing and large resolutions. With that being said, one graphics card should be enough for you, but make sure it has all the features you're going to need. Don't just go for the best overall card, go for the best gaming card you can get. If this is a gaming system, make it a gaming system, not something you're going to use photoshop, flash, or burn MP3's and DVD's on.
Good luck with this, and hope everything works out well for you.