[This part is more of an aside, since not sure the "end purpose of the bpm...]
I put a similar
feature request out about a month ago for the same reason as the OP. For me, AudioSnap requires excessive overhead and has been rather flaky with results even when feeding it properly. Within AS, it would be nice to tweak the algorithm with an audio microscope, but this still requires "man handling."
The real reason I had posted that request was I had picked up
Riffstation (still on sale, with a trial version available) and was randomly opening commercial masters (not individual tracks) and the bpm was correct in far more cases than AS gets, and I needed to do nothing more than open it. I was incredibly dismayed to see this since many of the ones I eventually opened did not have highly defined percussion/bass.
I just got that VST to play with it, but its ability to extract accurate bpms stuck out the most (each file must be opened discretely, of course).
[end of the aside... more FYI unless "just average bpm" is desired]
[Most practical method within SONAR...]From another standpoint... if importing an old wav file, using Shift-M to define beats in the song is the best method I have found to set a tempo map for the project. Is fairly clean and quick. Once that tempo map is set, the song can be embellished with MIDI/VSTis easily.
Using this method, you can open a song, lock the first beat of your choice, then go out several bars and lock that one... the region between the two will have the bpm you have set (manually), but if importing a wav and intending to embellish it, using Shift-M throughout the song is the best way to accurately map the tempo (since it can easily have variations to throw off MIDI).