I had a new 4B-ST that I bought in Montreal for about a year driving a pair of used Thiel CS7s and, though the combination worked very well, on some recordings with a lot of bass, I could get the amp to start lighting the clip LEDs at not very high volumes. Moving to 7B-STs solved that problem. Then again, the 7s are about as tough to drive properly as anything out there. As long as your speakers don't dip below 4 Ohms at a minimum impedance (CS 7s went down to 2.3 Ohms as I recall), you'll be fine.
