While I haven't heard the Rowland 112 amp, I've hear good things about them. I have used the Pass X150 in a few systems now, and can say that it definitely will be a fine match with the Proac 2.5's with good gear all around! That X150 is as good as you can expect for anything under $5K. I used to have a pair of Proac 1SC's, and have owned the likes of Thiel 2.3's while using the X150 in the past, and it's strong!...and refined ofcourse. Knowing the sound of the 2.5's alright, I think you will be very happy.
On the other hand the Rowland is probably in the similar league, or at least close. Perhaps some one else can shed some light on the differences. Good luck