Ezaudio, in the first generation of X amps your 250 was the best sounding of the three two channel amps by far. I don't know if you talked to Peter or Kent at Pass, but when I did they both agreed that the new 350.5 was the new "sweet spot" in the two channel amps. The difference is not a minor one in the X-.5 series compared with the first generation but adds great musicality/warmth without losing the great dynamics/speed of your amp. The 350.5 replaced an Edge NL-10 in my system that was/is a great amp but could not do some of things the Pass Labs can. You could ,if your interested, look up my review I wrote for the GON that will give you more details then this short post. So, my opinion would be is that either the 250.5 or 350.5 would offer you a real upgrade compared with your terrific 250. I have not talked to anyone yet who has replaced their X amps with the new X-.5's amps that have not been wonderfully pleased with their new amp. Hope this helps.