How much do you want to spend? You can get wiinippongamer's build and it would be a good build (I recommend getting 4 GB ram, though) but if you don't want to spend that kind of money you don't have to.
What motherboard do you have now, and what is your budget.
The rig wiinippongamer has suggested is nice, but it is a big jump to a complete new build, and spending a GRAND on an AMD system.
Lets look at some other options, holy cow.
Tnx For the reply. Your Build was way more better than i said earlier.
But May I ask if a 500w power supply can Power all of the components u mentioned?
And if i Really need that kind of expensive motherboard?
depending on the psu, a crappy, non-branded psu that explodes when you push it's labeled wattage won't run any of those cards, while a quality antec 500w or corsair 550w will most likely run up to a single 5870, but for the dual 4890s you'll need some more, i have 2 4890s on a 750w corsair, some people recommends 850w or more for that, but as i have just 1 hard drive and 1 dvd burner they work flawlessly with the 750.
but the kind of people that has 4 or more hard drives and 2 dvd burners WILL need more
you don't really NEED that kind of motherboard, but if you want to have 140w cpu support, up to 16g ddr3, 4 pcie 2.0 instead of just 2 that most mobos has, REALLY good overclock and CrossFireX support, alot of sata and usb ports, some ide ports, very good onboard audio, and FAST memory support, then get this.
also it has 2 of it's pcie ports running at full x16, great for crossfire, while most mobos has one of its pcie running at x16 and another running at x8 or x4, so in those, the second card will not penform as good as it should, cause it'll be limited to half or less of it's bandwidth.
so it's all about expansion capabilities, if you're not going to run a second card then another motherboard would be ok.
it's not really NEEDED to have that all that, but they're some very nice features to have