Start here as well. The more info you can give, the better recommendations we can give you for your situation.
JSC gave some good basic suggestions to start with, too.
If I had $1600 -
CPU i5-2500K : $200 CoolerXigmatek Gaia or CM 212+ : $30 Mboard Z68 Chipset : $150 - $200 RAM 8GB DDR3 1600 : $60 GPU GTX 570 or HD 6950 2GB : ~$300 PSU FSP Aurum 700W : $120 SSD Crucial M4 128GB : $200 HDD Samsung Spinpoint F3 1TB : $60 Optical Asus DVD : $20 Total : ~$1200
That means you've got $400 left over for a case, monitor, and any extra fans or SATA cables you'll need. The 700W PSU will be enough for a single graphics card, but if you plan on SLI or CrossFire, you'll want to up it to 850W, and that will eat away more from the budget. The 700W could CrossFire 6870s, but if you're spending $400 on graphics, I'd rather get a single newer card and plan on dropping in a twin in a year if you want to keep it current.
At $1600 you won't be able to afford the best GPU, the flashiest case, the best mboard, and an amazing monitor. You'll have to cut back on one or more of those. Sacrificing the GPU doesn't mean you'll have sup-par game performance, just that you'll be playing them on high settings instead of "ultra." Sacrificing on the case and mboard means you won't get all the features you'd like, but you'll have enough for a solid system. Sacrificing on the monitor means you won't have the biggest, highest res display you may want.