Asimov - congrats, but didn't you just buy the 4B-SST/2 this past Nov. 2010? Why the change? Aren't you still using the Dynaudio C1's? Did you need more power?
Hope the 4B-SST/2 goes off to a good home. 
I'm not using Dynaudio C1 anymore, I bought Dynaudio Sapphire.
Sapphire is an easy load than C1, power is not the issue here.
So far I understand 7B SST2 would be better than 4B SST2 in overall sound quality.
I have had option to go for Accuphase A-65 but failed to love the sound of Accuphase.
I love the sound of 4B SST2 and took a calculated risk and ordered 7B SST2 without any auditioning.
I've listened to 7B SST but 4B SST2 is better due to squared version.
I feel squared version has some sort of warmth which is not present in non-squared version.
I was also considering 28B SST2 but it is almost double in price than 7B SST2 and I failed to justify
the price, 1K watt is not required for me. But who knows ........... it's a crazy hobby!!