I have not read through the hole thread so hope i am not repeating!
I would personaly get 2 smaller ssd, maybe the 60gb agility 3's and run them in raid. ssd speed for me has the most visable performance increase in day to day use. I would install the os on them along with all your other programs.
Put steem on your other drives! which is definatly possible as it is what i have done.
just my 2cent.