Set amps ?

Maplegrovemusic,
I would say the reason why well implemented SET amplifiers sound so good is due to a simple circuit that retains much signal purity. This results in a very natural sound and purity of music.

In the current 6 Moons.com there is a review of the new Avantgarde XA preamp. The chief engineer explains the mandate was to make the circuit as simple as he possibly could.
It has only one gain stage,only one transistor per side,no coupling capacitor or DC servo unit(it is DC coupled instead).He made the signal path wiring ultra short.

What is interesting is the reviewer points out that the Soulution 720 preamp follows and is built on this very similar 'simple' concept. It`s a good read if you have the time.

Nelson Pass has ventured down the path for quite some time with his First Watt amplifiers.They have become simpler and ever better sounding over the years. His latest S.I.T. anplifiers are the most simple yet and are said to be the best sounding of all the First Watt designs.

There is much merit in the keep it simple concept and SET represent the epitomy of that idea.The principle is lower the number of parts used while increasing the quality of them.That works for me.
Regards,

In addition to the power consideration, I would be cautious in pairing a SET amp with a speaker whose impedance varies widely as a function of frequency. See Figure 1 of Stereophile's measurements of your ProAc Response 2.5.

Basically, the high output impedance that SET amps typically have (corresponding to very low damping factors, damping factor and output impedance being inversely proportional) will result in increased emphasis of frequencies at which the speaker's impedance is high (in this case, particularly in the vicinity of 1 kHz), and decreased emphasis of frequencies at which the speaker's impedance is low (in this case, particularly in the 100 to 200 Hz region).

The fact that the speaker's impedance goes no lower than about 6.5 ohms at any frequency will mitigate that effect to some extent, but I would expect it to still be audibly significant with most SETs.

The excellent results Stereophile reported when using the Cary 805 SET amp with your speakers should not be viewed as indicative of the tonal balance that other SET amps would provide, because the 805's output impedance is much lower than the output impedance of many and probably most other SETs. See Table 1 here.

Regards,
-- Al

Art Audio Jota High Current (HC) has 24 watts per channel with KR 300BXLS tube, and will drive your speakers with no problem. SET amp sound is magical.

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.