I've got to say, I did consider a 36g 15k SCSI Drive for my next build, but it is likely that my next build will be an XBox 360, as my Desktop & Laptop are more than suited to all my non gaming needs.
Like TooNice said, it really is a cost issue. If it was no holds barred cost is no issue, then it would perhaps be my recommendation, but I still think you'd be better off with one larger drive.
That said, if you can find a controller, and you can afford to get a second storage drive, then for £45, you can't really argue.