Quote - I have a couple of ideas I think you should think about for that system.

First off get a third hard drive to backup on, something as big as the two 160's or bigger. make sure to seperate the hard drives as much as posible, and I like to use these on drive cooling fans as extra cooling. The raid bit makes the drives much faster but if either drive crashes you loose all the data on both drives, now the raid 10 bit with both mirroring and striping is good but in most cases a raid array for the programs and a third drive for data is a bit cheaper and some times more functional.

Put as many case fans in as you have spaces for, make sure to get a case with lots of fan locations and more drive bays the better too.

As too getting a premaid DEL, HP, whatever; I allways tell people a custom upgradeable system is better long term, as you can get new video cards, main boards, etc. and keep upgradeing rather than having to get a whole new system every time you need a faster/better machine; These package deals seem like a good deal till you try to upgrade and find you have to get special expencive parts from the manufacturer or get a new PC.  

Thanks for the excellent advice **pdq1234. ** My latest build plan incorporates everything you suggest, including one HD for the operating system, one for my personal files (including runtimes), and a third for backups.  In addition, I'm using the Antec 900 chassis which has 120mm intake fans in front of the two drive bay modules as well as a 200mm exhaust fan on top and a 120mm exhaust fan in the back.  I'm also opting for 800MHz Corsair RAM rather than saving a few bucks on the value select 667MHz flavor in case I ever decide quad core prices have come down enough to bump up my CPU.  Finally, I'm going with the Intel Bad Axe 2 motherboard, which can also take the quad core (though I'm going with the Core 2 Duo E6600 for starters.  So I think we're on the same page!  Thanks!