yes, my tannoy's are really amazing, I've owned wharfedale, B&W and Yamaha speakers and I must say the Tannoy is the best out of the lot. They dip down to as low as 30Hz, so like you said, i dont really hear to much of a difference with most tracks. But on the rap songs and some jazz tracks, it makes a difference.
But nevertheless the SVS PB12-Plus2 really shows its stripes when it comes to playing movies. Totally brings in another dimension to the home theater experience.
I'm considering retiring the Nakamichi, every way i think of it, Its really not possible to get the setup sounding great with the new sub. I'll probably give it to someone in the family. I'm now pondering over a Rotel preamp+poweramp combo or a fat Denon AVR-4806 and a pair of Klipsch RF-83s