How good is Pass INT25?

i have the xa25 which is the power amp section of the int25, i run a dac with volume control into it, so it is functionally working very similarly to the int cousin fed with a fixed output source

sonically, in build quality, and in terms of the company and people who stand behind it, it is absolutely superb, without qualification

whether it will please you more than luxman or sugden class a amps driving your speakers, i really can’t say

I believe the INT25 is basically the XA25 with a 6db gain buffer in front of it for a preamp section, so you can also use XA25 reviews as your guide.

I use Nelson's First Watt SIT amps with my Coherent speakers (which are also high efficiency like your Klipsch) and love it, so I would guess that the INT25 and Heresy IV would be a killer combo. Steve Huff reviewed the INT25 with Klipsch.

Great great integrated. I have one of them and have been an audio hobbyist for a long time and have owned too many pre/amp’s and integrateds. There is something unique and special about the "voicing" of the INT-25. I play it through a pair of Harbeth M30.1’s and for the style of music that I enjoy most (guitar, piano, acoustic instruments, etc.) it’s great match. Nice wide and deep soundstage with recordings that have these elements in the recording. Timbrally precise. Very much like having the instruments in the room. It does have to warm up for a bit 30 min or an hour but that’s a small price to pay. I can see this integrated being a "keeper".

I've also owned the Luxman L-550axii, a LFD NCSE and a Sonneteer Alabaster among lots of others.  They were great integrateds as well although neither the Sonneteer or LFD come with a remote control.  

On another Pass Labs note; I recently bought a SVS Micro 3000 subwoofer and realized that the INT-25 only has speaker outputs (high output). I called Pass for some advice and not only did I get specific advice from one of the principals of the firm (you’d know his name), but he went so far as to suggest a certain product from a small vendor that would be perfect for my use case. Really what can I say? American made product with old fashioned hi quality, real customer service. You simply just don’t get that kind of service from most other vendors.