Only you can decide if it's powerful enough. I have a 530i - in my opinion, the best blend of power and handling (the 6s use rack and pinion steering, the 8s recirculating ball, the 6s weight distribution is near 50/50).
I owned a 528i before that. I've driven, but not owned 540's. The power's a blast, but I've never been in a position where the 6 didn't have enough power for whatever situation. It's just not going to win drag races. It will cruise at 80 - 90 all day long, though.