Mozvz,
I haven't listened to the X250.5 or X350.5, but I own the XA 60.5. The pair of 60.5 sit on stereo rack. So it does not matter to me if I have 1 or 2 amps. The reason I write is that I don't think I'll ever come back to Class AB amp. after living with Class A amp. The mid-range is more much natural, meaning less harsh and more fluid. Sound texture is far more realistic. To me the sound of each note, let it be vocal or instrumental, is a continuum of frequencies with the dominant ones being more present and hanging around a little longer. The subtle frequencies thus have shorter transient. Class A amp., at least the XA 60.5, let me hear the whole spectrum of frequencies as opposed to mainly just the dominant frequencies. The result is a truer sound.
From the power standpoint, 60 watts/channel means 120 watts for my full-size speakers. The pair of XA 60.5 are actually more dynamic, with that headroom you are talking about, producing more slam yet distinctive drum bass than a 150/300-watt amp. they replaced. To avoid talking down on a well respected amplifier, let me say that this former 150/300-watt amp. of mine came highly recommended by Stereophile who put it in their Class A category (this is review rating, and is not the "Class A" amp. I referred to earlier). Now that should tell you something about the XA 60.5.
