If the amp is going back to Pass for repair anyway, perhaps you could just contact Mark @ Reno to set up an audition of the XA100.5 and the X350.5. I'm sure Pass and Reno could work out an accommodation as customer service is a top priority for them.
Scratch that, I just noticed you are in Singapore. The dealer should let you audition. If not, contact Pass and find another dealer. Should should hear the difference for yourself.
Scratch that, I just noticed you are in Singapore. The dealer should let you audition. If not, contact Pass and find another dealer. Should should hear the difference for yourself.