key point is that well built ss amps can double power output into 4 ohms versus their basic 8 ohm load rating... tube amps cannot do this and can struggle to deliver even the same power in 4 ohms versus 8...Doubling power is not the same as that amp sounding its best.
The reason is distortion- in solid state amps, this tends to be smaller amounts of higher ordered harmonics. Our ears use the higher orders to sense sound pressure and so tiny amounts of that distortion is perceived as harshness and brightness- and quite literally is why tubes are still around.
Steve McCormick has made amps that can easily double power into 4 ohms. But he sent a letter to Paul Speltz (known for anticables and also the ZEROs which are an autoformer) describing how in fact his amps sound better driving low impedance loads using Paul’s ZEROs (www.zeroimpedance.com). I described why above.
Of course, if you have a set of ZEROs to work with your four ohm Maggies, then you can use a tube amp pretty effectively as well. We are in the same town as Magnaplanar and so have a lot of local customers who use our amps with them. Our amps don’t have an output transformer (hence the term OTL) but the combination works quite well. In smaller systems our M-60s get used with the ZEROs.
The bottom line here is that no matter what amp you have, if it is driving a 4 ohm load directly, it will be audibly inferior to how it drives an 8 ohm load or even 16 ohms. The ZEROs are a workaround for this problem.
I know people will say that a big enough solid state amp will do better, but it does not matter the amp, you will see in the specs that its distortion is higher into 4 ohms. Distortion causes colorations (like harshness and brightness); high end audio is all about getting away from that. If you are really stuck on a 4 ohm speaker, consider a set of ZEROs no matter what amps you have.
