Disclaimer: Keep in mind that I am a pass labs dealer.
Yesterday I had a friend over to try out his magnepan 1.6's with my X350. It was an amazingly good match. The bass of the 1.6's came out like I've never heard before. It was so much more powerful that you would have thought that someone added a subwoofer. A very very good subwoofer at that. This was after we had been listening to the magnepans with my superb $9000 200 watt/8ohm,400watt/4ohm Ayre v1x solid state amp. The X350 puts out 700W into a 4 ohm load.
I've had a few sets of the 1.6's in my room and have hooked them up to around 10 different amps. Two amps stand head and shoulders above all others: The X350 and the Wolcott P220 EL-34 tube amps. The arc vt-100 is pretty good too.
Based on what I heard, I would recommend that you go with the X350 for the extra power. After several tries, we were actually able to get the power meter to move into class B. We used the Burmeister III drum track at medium loud volume. Sounded like artillery in the room. No other track came close to moving the X350 meter out of class A. With my 87db efficient Avalon Eidolons I barely see the meter move.
