Maximum PC

I'm ready to assemble a new set-up
Looking to the pros (yeah, you guys) for a nice MOBO/CPU recomendation.
Any additional sugestions a plus.
I'm a mid-level enthusiast.

I'd like to try the 64bit XP pro, if its a worthy improvement.
I like ATX & fond of AMD/Nvidia, but open to Intel,
I want 3GHZ++ of multi-core,
4 to8G of memory with good MHZ,
Should have 4 SATA ports & I'll probably use a 80G SSD for C:,
I have a nice GTX7900 but a video card improvement is welcome.
Nice to have a couple of old PCI slots.
What can you guys come up with, I'm shopping Newegg, Tiger & Amazon
Thanks

Oh, my primary need for performance is running MS Flight Sim X on a 52" LCD HDTV

I posted this earlier, should work for your needs as well, great price/performance game rig

Part list permalink / Part price breakdown by merchant / Benchmarks

CPU: Intel Core i5-2500K 3.3GHz Quad-Core Processor ($179.99 @ Microcenter)
CPU Cooler: Cooler Master Hyper 212 Plus 76.8 CFM Sleeve Bearing CPU Cooler ($19.99 @ Newegg)
Motherboard: Biostar TZ77B ATX LGA1155 Motherboard ($79.99 @ Newegg)
Memory: Patriot Signature 8GB (2 x 4GB) DDR3-1600 Memory ($41.99 @ Newegg)
Hard Drive: Samsung Spinpoint F3 1TB 3.5" 7200RPM Internal Hard Drive ($109.99 @ Newegg)
Video Card: MSI Radeon HD 7850 2GB Video Card ($259.99 @ NCIX US)
Case: Cooler Master Elite 370 ATX Mid Tower Case ($35.18 @ NCIX US)
Power Supply: Antec 650W ATX12V Power Supply ($54.99 @ Newegg)
Optical Drive: Samsung SN-208BB DVD/CD Writer ($28.98 @ Newegg)
Total: $811.09
(Prices include shipping and discounts when available.)
(Generated 2012-04-27 07:07 EDT-0400)

cheers

A budget of some sort would help frame our responses to give you the best advice.

I would change one thing...the Case! Fractal's Arc Midi is the one I chose and is comparable to the antec but in my opinion nicer. I just built into this case and I'm completely happy with it. It does have some drawbacks though. No removable motherboard tray, but with the new coolers I'm not sure this is an issue. The other main issue is that only the top hdd cage is removable, which in my build is sitting on the shelf anyway. I've paid a lot more for cases in the past and they were junk in comparison. I got it off the shelf at a micro center for $89.99 but it was on sale.

http://www.newegg.com/Product/Product.aspx?Item=N82E16811352007&Tpk=fractal%20arc%20midi