My understanding, and I am pretty much pulling this out of my ass, it that the first four albums sold total about 20,000 copies each. When BWP came along it was the big breakthrough, selling about 80,000 worldwide. I don't honestly know about D1/D2. What I do know is that Opeth are now amongst the biggest bands in underground metal, which is a bit of a shock to me, were you to tell me that 5 years ago. People who don't really know underground stuff are starting to have at least heard of Opeth. I see random teenage goth girls with Opeth stickers and such now. It's all very strange to me, I always pegged Opeth as the one band I could rest assured NOBODY I just randomly met would be into. No longer the case...