wanna buy the best gaming pc

The second most expensive computer is what you need

A gaming machine can easily exceed $5,000, and with customizations even more than that. (There exists a graphics card that costs $2,500 alone.) Thus, your price range is an essential starting point. Perhaps also what games you plan on playing...you don't want to pay top dollar if you could get the same performance at a fraction of the price.

Let us know.
John

In the $2000 range, anything over and you've gotten into sales gimmicks or excessive monitor configurations. While 30" LCDs that can do 2560x1600 may LOOK cool, theres no Direct3D capable graphics subsystem in the world that can handle 2560x1600 in modern gaming with any decent performance (8800 Ultra SLI can get close, but seriously, $1700 just for graphics cards is somewhat insane).

AMD used to hold the title of being "the choice" for computer enthusiasts, but Intel's Core 2 is just too good to ignore. The Core 2 Quadro is dropping in price in about 20 days, bringing quad core processors to the $250 price point (AMD doesn't currently offer a quad core). Quad cores are beneficial for Supreme Commander, and digital content creation, most other games won't benefit hardly at all, however the Core 2 is still very capable (its faster than Pentium 4/Pentium D and Athlon64 in terms of mhz for mhz, the extra cores only help in some areas though).

2GB should be your minimum buy point, 2GB of DDR2 costs about $120, so theres no reason to go any lower than 2GB of RAM. PCI Express x16 should be the standard for graphics, AGP is dead in the water, I'd suggest looking at the GeForce 8500, 7600, and 8600 series (listed slowest to fastest) along with the Radeon X1600, X1650, and upcoming HD 2600 series (listed slowest to fastest). A system along those lines should only cost about $900 to $1000 with case and decent power supply (I can't stress enough how much getting a high end power supply is important, don't waste time with "500W for $29.99", it isn't worth it, I'd suggest looking exclusively at: Antec, Corsair, OCZ Technology, Enermax, PC Power & Cooling, SeaSonic, and Thermaltake).

The monitor is your next concern, as a bad monitor will make your gaming experience less than stellar, I'd suggest 1280x1024 or higher on a 17" or 19" LCD, go widescreen if you want, but realize that games which don't support widescreen (older games) will be streched. Also realize that games that can't be run at widescreen due to performance issues (like FEAR) will have to be run at a lower resolution, and be streched.