Wow, so many items to comment on... where to start?
Water cooling? No. Bad idea.
Seagate SATA Drives are a great way to go for quiet drives. Go learn a lot about RAID to understand the impacts of what you'll be doing. SATA RAID is a great solution for desktop systems. RAID 0+1 (aka RAID 10) is probably your best best for speed. RAID 5 is good for safety and READ speed, but takes a hit on writes. I did a stint as a DB2 DBA and IBM's information for DB performance suggests using as many spindles (drives) as needed to make sure that every the heads have just enough time to be in place for their turn to read data. To do that you need to calculate transfer rates, seek rates, block sizes and a bunch of stuff like that. You can spend weeks testing for optimum performance. Or you can use RAID 0+1
SCSI is not going away... in the server world at least. Currently SATA drives are not being built to quality spec to be used in a serious environment. They're great for you and me to use on our systems, but when downtime and failure are not an option, you almost always use SCSI. Check the drive specs and you'll see a difference in RPMs, bearing types, MTBF and stuff like that.
Watching TV on your new box? I just bought an ATI X600 All-in-wonder. I'm a lot disappointed in it's performance. They have a know problem with dual and/or hyper-threading processors. They're working on it, but I really expected much better performance out of my PCI-X card than my old AGP Version. Not seeing it. Either way, I like ATI over Hauppague (sp?).
Dual monitors... I just went dual head too. I'm not in love yet. I gave up a really nice 21" monitor (1600x1200 true color @ 85Hz) and went to dual 17" Acer monitors (1280x1024 true color @75 Hz). Although my screen real estate should be much larger, it just doesn't feel bigger.
Finally, you should google for "every OS sucks" and watch _Three dead trolls in a baggie_ perform their smash hit. I found it several years ago and recently rediscovered it. It's amazing how true comedy can be.
PS: Get a couple of Gigs of DDR2 RAM at least. With stuff like the VMWare player around, you might find your RAM needs going up a lot. DDR2 is a nice boost in speed.