I've owned Harbeth SHL5's and currently own my 2nd pair of 40.1's. In my experience, the two speakers don't have much in common. The SHL5's lack the warmth and organic, full bodied musicality that the 40.1's excel in. The original poster should not let their experience with SHL5's taint their perception of how 40.1's would sound.
Both the 40.1 and 40.2 are relatively easy loads, so unless you have a huge room and listen at high volume, you'll be fine with any high quality amplifier in the 70 to 150 WPC range. I strongly prefer tube amps, but have had success driving 40.1's with all of the following amps:
- Music Reference RM9 MK2 (current amp)
- VAC 70/70 Signature
- McIntosh MC275 MKV
- VAC Phi 200
- Plinius SA-102
- Bryston 4BSt