You can get 160GB x 2 (haven seen any 320GB model yet) and RAID0, even faster.
Provided your Mac Pro support RAID.

Cold Boot =/= Sleep

Sleep still drains battery, and if you're on the road with your netbook (even if it has a 6cell battery) without your charger for days, Sleep will eventually become completely, utterly, battery-drainingly useless.

But I completely understand your point ... Even after the desktop appears you're can't really do anything on Vista cos your disk is busy thrashing itself like a doped up simian crack-hoe, rendering it unusable for the next minute or so .... hence your need for Sleep/Resume.

Lastly, your 1sec wake-up-from-sleep time is bollocks. No version of windows I've tried (not even win 7 on a Core i7) can wake up to a usable desktop in 1 sec. Actually, no version of any OS can wake up from Sleep/Suspend in 1 sec. Granted, Linux is pretty bad with wake up times, but even OSX Leopard and Snow Leopard (reportedly the best at resuming from sleep/suspend) still takes more than 1 sec.

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Added on November 9, 2010, 1:24 pmActually, in my experience, a single high-speed SSD  (like those from Intel or OCZ) on a SATA-II interface still has better random access times compared to a RAID 0 setup (even if the HDDs are 10,000 RPM). The RAID 0 setup has an advantage for Read/Write, though (but not by much). So it all depends on what he's using his MacPro for. If his job involves a lot of compiling, then the reduced bottleneck of a SSD will definitely be a better complement to his high-spec processor. If, on the other hand, he does a lot of photo editing or image manipulation (Photoshop, Corel Painter...etc) then the RAID 0 is probably the better (and more economical) setup.

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Added on November 9, 2010, 1:41 pmI can't help you with prices since I currently reside in Singapore.
With regards to brands, Intel and OCZ are the only two brands I've ever considered for my main desktop/workstation. If you can afford it (and want the mega-performance), then something like the new OCZ Vertex 2 with its SandForce SF-1200 controller will probably be the most suitable. I think the biggest size I've seen in stores for that particular model is 240GB (though their website claims to have up to 400GB models), but it's bloody expensive (most people will say it's not worth the money)

My main desktop/workstation currently houses a 60GB version of Solid 2 SSD (slower than Vertex 2), plus a standard 320GB HDD. I usually set up my partitions (I run Linux/BSD) to have the /Root partitions (I have 2 OS'es installed) take up the SSD and /Home, /tmp, /var partitions take up the HDD.  Perhaps you could do something similar with your MacPro (I have no experience with multipartitioning OSX, nor do I remember what journaling system it uses, so I can't help you there).

Cheers.