Let's keep it simple...
The logical upgrade from the B&K 7250 is the Bryston: perhaps two of the new 6B-STs (3x250); with these, you can provide exceptional power to the fronts (2 mains & Center) and the rear 3: this also provides the opportunity to put the rear-speaker amp closer to the speakers: a longer digital cable, shorter analog cable. This arrangement provides much more power to the speakers.
The logical upgrade from the B&K 7250 is the Bryston: perhaps two of the new 6B-STs (3x250); with these, you can provide exceptional power to the fronts (2 mains & Center) and the rear 3: this also provides the opportunity to put the rear-speaker amp closer to the speakers: a longer digital cable, shorter analog cable. This arrangement provides much more power to the speakers.