Im an old Infinity guy. If you mean a tube sound that has a warm bloom, a palpable silky sound with that continuous rounded sound, then many new tube amplifiers do not sound that way. Here is what I have used on the Infinity RS 1B and RS 2B. I use a Audio research LS 15 with two stereo power amplifiers, one being a Parasound for the bass; here, I just need good fast slam, a Bryston 4SST would be best for the RS 2B. The midrange and high I have a Class CA 200, which is not the best, but it is warmer than the Bryston or Parasound. B&K would be an ideal choice so would the Lamm, although Lamm are very expensive and not all that powerful. The problem is you need to think about if your speakers need to draw more power when part of the bandwidth has lower impedance. The solid state high current amplifier is best here because it will offer this. Consider the Nelson Pass products put out double power when impedance is half. The best amplifier solid stake does have this ability to double power and impedance double downs.
The Magnapan newer models I do not know much about. I am similar with the old ones and they were not that hard to push, but if they need this high current ability, then you have to choose a solid state amplifier that will increase power as the impedance drops. Consider the old solid state McIntosh amplifiers; they have taps that you set by the impedance you need, thus they do not have the ability to produce a higher current at less impedance. The only way around this is to use an amplifier that has the most power you need. I think the VTL 250 would be plenty of power unless the speaker you have are very inefficient or you like very loud music. Two amplifiers that I have actually owned that were beasts are the Threshold T 400 and the Krell KSA 250; they hold to class A at a very high wattage, more than the newer ones and they also get very hot and used a great amount of power even at idle.
If you like the more musical not at all grainy sound, the VTL and ARC are good choices, but so are the high current solid state amplifiers. If you want the warm bloom and palpable sound, which I see as tube-like, then The older Marantz and McIntosh is best, even some old tube receivers, such as Fisher is great. Conrad Johnson is what I found closest to this as are any single ended tube amplifier, but they are not current flexible. If you can afford it, try the VTL, the ones that you can run in triode and ultralinear. Consider the cost of some of these amps!
