m17 vs m17x

[M17]
Dual 512MB ATI Mobility RadeonTM HD 3870 - CrossFireXTM EnabledIntel® CoreTM2 Extreme Quad QX9300 2.53GHz (12MB Cache, 1066MHz FSB)
17-Inch WideUXGA 1920 x 1200 LCD (1200p) with Clearview Technology
Windows Vista® Home Premium (64-bit Edition) with Service Pack 1 (difference vs ultimate? :()
4GB Dual Channel DDR3 SO-DIMM at 1066MHz - 2 x 2048MB
Dual Layer Blu-ray Disc Reader (BD-ROM, DVD±RW, CD-RW )
Single HDD configuration vs extreme performance Raid 0 (not sure which to pick, not sure what raid 0 offers that makes it more $$$
M17= $3,699.00

[M17X]
Dual 512MB NVIDIA® GeForce® 9800M GT - SLI Enabled
17" WideUXGA 1920 x 1200 LCD (1200p) with Clearview Technology
Intel® CoreTM 2 Extreme X9000 2.8GHz (6MB Cache 800MHz FSB)
4GB† Dual Channel DDR2 SO-DIMM at 667MHz - 2 x 2048MB
Dual Layer Blu-ray Disc Reader (BD-ROM, DVD±RW, CD-RW)
Intel® Turbo Memory (1GB) - Accelerate Data Transfer Speed (only available with single HDD configurations, vs raid 0 (still not sure what it does :()
Same OS

M17X=$4,999.00

So basically, i'm not sure which one of these to buy, i have been out of the PC gaming scene for a while and am not sure which CPU,GPU, or HDD setup is better, everything else in both these setups is pretty much the same. I have no idea what Raid 0 is and if it is worth the upgrade and im unsure if vista ultimate is worth it either. If you guys can, let me know what you think of each setup and some good ideas of stuff to change,remove,add w/e. let me know what these things will and wont be capable of, thanks a lot

[QUOTE="Goldeneyemaster"][QUOTE="creekfan_basic"]

[QUOTE="inter_911"]2400ms is just very expansive for a small expansionlimpbizkit818

but you will pay over double that for 10 hour games like Gears, Fear, etc?