Shannere, the obsession with ratings is that if you have 4 ohm speakers, you could run them with a 500 watt amp that doubles down into 4 ohms without worrying about circuit breaker problems. The whole point is moot if you're running 8 ohm speakers. If you've got 4 ohm speakers, someone had better answer some questions and document it. I have a set of Infinity Kappa 9's that dip to 1 ohm and below. I'd certainly like to know if the amp has the testicular fortitude to handle those low impedances for sustained periods without bypassing the circuit breaker on the rear of the amp or worrying about tripping the house circuit breaker. I'm sure someone that owns a set of low impedance amp-killing Apogees would certainly question this amp's performance at 4 ohms and below. Krell lists its amp at 900 wpc @ 8 ohms and 1800 wpc rms @ 4 ohms.
Sorry, but when putting out that kind of scratch, I'd like to see its 4 ohm performance in writing.
The 7B SST states that it will go to 900 wpc @ 4 ohms. Something tells me that the 28B SST won't perform any better at 4 ohms. So, if you've got a 4 ohm speaker, you could probably save yourself some dough and go with the 7B and be assured of your 4 ohm performance. I still see question marks all over the place for the 28B.