I have a 2001 530iA (Steptronic) which has been driven in the Sierra Nevada mountains, Lassen Volcanic park, the steep hills of downtown San Francisco, California's Highway 1 along the Pacific coast, etc. etc. I can tell you confidently that the 530 has plenty of power (torque, actually), even climbing through 8,000 ft. (I drove a previous Nissan Maxima to 14,000 ft in Colorado. At that elevation the fuel/air mixture ratio interferes with performance.)
The new 545i, with 325 horses, has about the same output as the M3 (333 bhp) and is a bit shy of the 393 horses of the M5, with a price that falls in between the two, filling an ideal "midlevel" position in the lineup. The former 540i was rated at 289 bhp if I remember correctly. For me the decision was either between two cars -- a commute car and a weekend car -- or one that would fit both bills. After much debating (decisions decisions) I chose the latter option. I suppose I'll switch to the 6-speed manual and pretend it's a baby M5.