I have used my Super HL5 Plus with Rogue Audio M-180 monoblocks (180 WPC) and currently ARC VSi55 integrated (50 WPC), both are tubed. I use solid state with my Harbeth P3ESR - Simaudio 600i (125 WPC). I agree that you don't need a ton of power.
What exactly do you mean by "underpowered"? If you want to have rock concert levels these may not be the right speakers for you.
What exactly do you mean by "underpowered"? If you want to have rock concert levels these may not be the right speakers for you.