What is wrong with the Pass you now have?
It's an excellent amplifier and I've really enjoyed my time with it so far, but it's not flawless.
1. It's a very high performer, it's got a very spacious soundstage, wide deep and tall, with excellent layering and separation. It has large vivid and palpable imaging. The bass is huge and lots of fun. But at the end of the day, it's slightly too coloured for me, and despite the warmth, the mids still lack some of that sweetness and purity that the Quad had. There's still some dryness to the PASS X250.5's mids.
2. It has quite low input impedance at 12k ohms. That means there's some bass roll off with the tube preamp that I have currently. I could ameliorate that with a higher uF value output capacitor, but I would like to avoid soldering and I'm worried what a higher value cap would do to the sound. Buying a new amp is just easier, one with higher input impedance this time.
3. It takes quite a while for it to warm up and reach peak performance. I don't like waiting around that long, especially when I've had a long day at work and just want to kick back and listen to some music. I'd also rather not leave it on 24/7 because it's an older unit and I don't want the capacitors to dry out (plus the energy bills add up over time!)