$1500 will buy you a lot of computer, even starting from scratch. Start with recommendations from Tom's Hardware.
http://www.tomshardware.com/reviews/core-i7-sff,2312.html
Skip the micro ATX X58 Mobo; no need unless you're building a small profile PC (which will run into airflow/heat issues when overclocked). Won't bother recommending a case since I have no idea if you plan to recycle or what form factor you prefer or how much of your budget you want to sink into it.
Tom's has plenty of good recommendations for X58 boards based around an i7 build (920 offers best bang for buck at $280 when overclocked). There are now quite a few under $200 that should cover your needs.
http://www.tomshardware.com/reviews/cheap-x58-motherboard,2368.html
For best price/performance with overclocking, the AS Rock X58 Extreme ($170) should be near the top of your list.
Higher end boards can exceed $300, eating a significant chunk of your budget for features you may not use or need. Probably better spent on faster video cards instead.
http://www.tomshardware.com/reviews/x58-motherboard-i7,2164.html
The Asus P6T Deluxe (under $300) is a very popular X58 board for system builders, but supposedly it doesn't actually support both Crossfire (it does) and SLI (does not). Check to confirm first if you're planning on using Nvidia cards.
For $1500, skip the GTX260 Core 216 and go with a pair of GTX275s which will give you the same performance (or better) than a $500 GTX295 at a lower price.
The GTX295 should be reserved for higher end builds than your budget permits that plan on going quad GPU. You can always buy one today and add a second later when they're cheaper naturally but one still costs more than a pair of GTX275s today.
If you prefer ATI, then a pair of HD4890s will give you very similar performance to a pair of GTX275s.
Other basics should be 3x2GB 1600mhz DDR3 RAM, 1TB HDD for primary (RAID config or 10K boot drive is up to you for extra) a 750w supply (many would use a 1000w supply which is overkill for this build; better to spend the same amount on a higher quality 750w PSU instead), whatever type of optical drive you want ($30 for your basic DVD burner, about $200 if you want to add a BD burner for whatever reasons).
I'm not doing the breakdowns and totals because there are too many variables depending on available deals at the time and individual selection of specific components, but that's about a $1500 build, including the $100 OEM Windows license which should be X64, recommending Windows 7 (due October); don't know your time table for putting this together. If you can still get the discounted upgrade installer, order that. Upgrades are $50 for Windows 7 Home Premium, $100 for Business which is as cheap as it will ever be.
Big disclaimer: All info on video cards is CURRENT. Windows 7 will bring DX11 to the table and with it a new wave of DX11 compatible video cards.
However, the pricing will likely be similar ($500+ will be your top end dual GPU, single card, top end single GPU cards will run between $200-300 or a bit more).
Also, for a strictly gaming rig, the i7 isn't actually essential, but will give you the best in terms of longevity. Doing a high overclock on an E8500 dual core system ($180 CPU that can easily be overclocked over 4ghz on air) may be near ideal for today's games, but very near future top end games may start making full use of quad cores, and none is faster than the i7.