Head,
As you well know, NHT can often times produce a very fine and solid product. I paid full retail for the SB-3's (first time I have ever paid full-retail for an item). Regardless, the value is still there in spades. I am considering trying out some Triangle Titus 202 bookshelf speakers. Rumor has it they respond very well to tubes, and mix well with NAD gear. As good as the SB-3's are, they want juice and a lot of it.
I am curious, do you set up this rig for professional mixing, recording, and playback, or is this a system catered more towards where you listen to most of your music?
I built myself a sealed sonotube for a sub. It can shake the house if it wants, but accuracy was the name of the game there. You can loose spl, but you certainly do gain control.
I have no real quality bass evaluation cd's. Just a song here or there. Most of the other "bass tests" is synthesized stuff or sine waves.