Doug - I ran in the Supernova Classic for probably 6 years, injury free. Same deal - narrow heel, liked the lowish heel. I too stockpiled.
I tried the 'replacement' shoe, but it was much more of a motion control shoe and not as narrow. I think it is called the adapt.
I moved to the adizero tempo and am very happy with it. I actually have two more pairs of the snova classics in the closet that I am not not looking forward to running in because I like the tempo so much. (size 12 if you want them)
The fit is similarly narrow, so that should be no problem. The difference is that the tempo is less of a stability shoe - definitely has less control and less cushioning. But I got used to that and now prefer the tempo. The snova classic feels bulky and heavy to me now.
Sizing is the same.
there are two tempos out now - last year and this year - they are pretty similar.
I also like the DS trainer, although it is not quite as narrow as the tempo. But the DS Racer is narrow enough if you need a racing shoe.