I can see your concerns as its a big decision and a big purchase. But if the car is primarily going to be used for drift then you'd be hard pressed to go passed the SD's. The valving of the SD's are specifically suited to drift, with the spring rates to match. If i could offer one piece of advice it would be to copy someones setup that works. That might sounds stupid as everyones driving style is different, but that's what i did with 'Simon-R32's setup, as i knew it was a proven performer. I just customized it to suit my driving style. Like you said, you think my car has too much body roll, that could be tuned out with thicker swaybars etc.
I got my SD's from Japan for $2000 delivered. At the moment, one of the sponsors on NS has them advertised for $2610 plus shipping.
Email Streeter for a price http://www.jessestreeter.com/