Parts Preferences: Intel CPU, best GPU regardless of brand
SLI or Crossfire: Yes, unless a better option exists
Monitor Resolution: 1920x1080 (don't have a monitor yet)
I live outside the USA. I am building this PC from scratch. There is a listing on eBay that caught my eye,---an Intel 2600k cpu that is guaranteed to hit 5.0~5.1 GHz upon OC'ing, is it a bargain or a hoax?
Theres no way someone could guarantee 5Ghz with the chip only. It depends on your PSU, cooling and motherboard too. Also, i wouldn't bother with an i7 for gaming. No matter how high your budget is it just isn't worth it for gaming, it's more aimed at workstation PC's. I'd go for an i5-2500k instead. I could suggest a build but it would depend on your budget. No matter how high it is though, i wouldn't get any more than:
2x4GB 1600Mhz Corsair/G.Skill/OCZ
~120GB SSD (Think the Corsair Force one is meant to be good.)
Gigabyte GA-Z68MA-D2H or equivalent.
Antec 902/1200 or HAF 922/932/X are good choices
2 x GTX 570 or 2 x HD 6950 (If youre really determined to spend more than that then go for 2 x HD 6970 or 2 x GTX 580 but i wouldn't go for a GTX 590 or HD 6990)
If you intend to get a high end intel based PC for gaming with SLI/Crossfire, it's pretty much a given that you are wasting at least some of your money if you are only running your games at 1920x1080 or 1920x1200. A single card solution can easily handle that with everything maxed out. So if you intend to reap the benefits of such horsepower, either go with multiple displays like say 3x1920x1080 or a single 30" 2560x1600 which will take use of the horsepower in the machine. 2x6970 or 2x580 will be able to generally run your games at 2560x1600 pretty much maxed out.
Other than that i think the basics were already drawn by jmsellars1 for gaming. Generally I would say 1000W+ on the PSU in case you do intend to run SLI/Crossfire of the very highest end.
I would however like to add other choices for the cases:
Corsair 650D/700D/800D great clean and simple black cases with wonderful cable routing.
The frontpanel connectors and the sata backplanes can be updated to USB3/Sata3 so don't let that stop you
Lian-Li also has some options in the $200-250 range the cases being full aluminum. More of a looks thing though.