Did you audition another X150.5 in your system before buying your new amp? If so, and assuming it was broken in, that is the sound you can expect. If you did not audition one before hand, it might be difficult to know what to expect with your particular gear. I don't have any experience with the X.5 series.
I do own XA.5 amps and found that they became more effortless, smoother and more detailed after break in. They are anything but sterile and uninvolving in my system. The improvement is similar to comparing my amps right after turn on to a couple hours of warm up. My amps were demos and as I recall sounded pretty good when they first arrived. I played them for 100-200 hours before they were really well broken in and they sounded even better.
I do own XA.5 amps and found that they became more effortless, smoother and more detailed after break in. They are anything but sterile and uninvolving in my system. The improvement is similar to comparing my amps right after turn on to a couple hours of warm up. My amps were demos and as I recall sounded pretty good when they first arrived. I played them for 100-200 hours before they were really well broken in and they sounded even better.