"traditional" and "progressive" don't necessarily fit very well together...
however...
contradictory statement... or at least it SHOULD be... this is where all the confusion comes in
the terms "prog" and "progressive" are SUPPOSED to be the same exact thing, prog just being an abbreviation... but as you can see, your own interpretation being an example, they've sort've taken on their own separate meanings
apparently if you make long songs, use keyboards, and solo a lot, you're a "prog" band... e.g. Dream Theater and Symphony X... both referred to as "prog" metal yet neither band is progressive
I will stick true to picking Enslaved as my answer to this thread... they're progressive, "prog" or not
Sigh, another great progressive metal band
Opeth, of course