Set amps ?

As usual salient comments from Almarg. I would agree this Proac speaker is`nt a likely choice for 'lower' power SET amplifiers.However there are some SET models out there that will mate with this speaker superbly. Too bad that it`s usally difficult to get these various amps into your system and hear for your self. As Jburidan says the sound can be magical(with the right speaker).
Regards,

The Response 2.5 works great with our M-60s, but as I recall some customers could run them (60 watts) out of power, although they were in a large room. 6-8 watts just won't be enough.

I love single-ended amplifiers but I've run into matching problems with lower efficient speakers. Even a homemade 15W SE (ultralinear in this case) amp with negative feedback couldn't drive a pair of current hungry Magnepan speakers to any reasonable level. But they did sound quite magical at low volume.

But the same amp on 91dB KEF speakers makes plenty of volume - in my friend's smaller living room.

So if you like head-banging levels or big dynamic music, then SE amps may not be the way to go, unless you run some "big powered" 805/845/211 amplifiers or get more efficient speakers.

Maple,
Most here agree, if you decide to try a SET with your speakers you`ll need the higher power versions(with good transformers and beefy power supplies).

what was magical, albeit not tubes, was Rowland with 2.5s. A simple Concentra was sublime on them

of course, ARC is what they are designed with.