Oldpet, I think there are a lot of misconception about tube amps. They can have just as much slam as SS amp. It really depends on circuit and parts used in the design.
Same applies to SS amp. Jeff Rowland is more refined sound to my ears.
I'm currently using Lafayette KT-550 amp ( a non-ultralinear version of HK citation II ) and HK Citation I preamp with home made cable to drive my 80db ATC SCM10 original version. It has more slam and fuller body sound than the Bryston and your Krell amp I heard with this same speaker. One thing I didn't like the Krell is grain. It drives with punch but lack of refinement. The transient sounded quick but very un-natural. The Bryston just sounded too thin and light weight with my ATC.
Many of the tube amps use low current power supplies, that's one of the reason why you don't get the slam you're looking for. Poor power supply also lead to poor sounding. I stopped by xyz audio shop in NYC and heard the Vac PA90 (with 4 X EL34) with BW 802s. Big sound but very poor bass control. The speakers are drawing too much current where the amp couldn't handle it. This is exactly what I mean by suffering from PSU. Even with expensive cables, it didn't help the sound much.
Unlike SS amps which all have high output rating, proper power output matching is critical for tube amps.
