Best bang for $ upgrade

Hello,
My current system (since 2008) is:
ASUS P5E VM HDMI, Intel Core 2 Q6600 G0 2.4GHz, 2G 667MHz RAM, Nvidia GeForce 8800 GT, Seagate 250 G * WD 320 G RAID 1 (ie 250 x 2),
Generic 500 W PSU, XP Professional 64 bit

My main uses are surfing, Photoshop Gaming Crysis, Far Cry
(only 20 % of use)

I am planning to upgrade to:

XFX nForce 750i SLI Extreme, Overclock the Q6600 to ? 3.4G, 4 GB 800 MHz DDR2 RAM, 2x GeForce 8800 GT in SLI, 2x WD 500G SATA (RAID 1)
Ultra LSP750 750 Watt PSU, Windows 7 Home Premium 64 bit

I have some basic knowledge, have always had homebrews but am not a fanatic. I
upgrade modestly every 2 -3 years, but I'm always 2 years behind the curve
with the new hardware

I am a bit unsure of the best way to proceed. Here's my plan:
Install all the above components except the 2nd 8800 GT (Add later when the system is stable)
Install Windows 7 from CD
copy over essential Data files from previous IDE drives (I have the transfer cable)
Add 2nd GT 8800
slowly OC the Q6600 as far as it will go.

My aim is to improve the performace as much as I can while retaining my Q6600 and 8800 GTs
I think I can achieve 22000 on 3D Mark 06, which is double my current speed, and about 90% of possible.
How does that sound?
Thanks! Mike.

You might wanna looking into getting an SSD harddrive. It is a huge upgrade in terms of speed of the system.

Thanks for replying.
Not even if the 8800s are in SLI?

I'm not that worried that I might reach 22000 or might not.
I do know that it's going to be a LOT faster than what I have, for not a huge investment.
Are you suggesting moving up to an i7 CPU?

Upgrading the motherboard just to add another so-so 8800GT is questionable. I would just keep your current motherboard and upgrade to a single worthy current GPU like the 5850 or 5870. I'm willing to bet you'll be disappointed with the performance of SLI 8800GT's.

OK, so if I am disappointed with the SLI 8800 GTs, I can still use the 5850 with XFX 750i, right?

Technically, yes, but I don't know why you would want to. The Nvidia Nforce chipset boards are not stable boards and don't support Crossfire. Why are hung up on upgrading the motherboard? If you're going to upgrade the motherboard, I would get a quality P45 chipset board that supports Crossfire with the 5850. Here's a very nice P45 chipset board.

GIGABYTE GA-EP45-UD3P LGA 775 Intel P45 ATX Intel Motherboard - Retail $129.99 - $20 MIR

Thanks Guys!
I'll rethink along some of the lines you have suggested,
Only 1 other question:
The 5850 is a pretty fast board. It looks like it's the fastest ATI board when not in CF mode.
Would anybody crossfire the 5850?

in terms of performance
5970crossfire
gtx295 sli
5870 crossfire
5970
5850crossfire
gtx285sli
gtx275sli
gtx 295
5870
5850
gtx285
round here is your 8800 sli idea
gtx275