Are Pass Labs amps probably the best ever you can buy ?

I have about 15k to spend on an amp/preamp/integrated amp.

I mostly listen to smooth jazz like Dave Koz, Rippingtons, Brian Culbertson etc.... and loud.

I have yet to hear any amp that comes close to Pass Labs.

Your experiences pls ?
yes, I love my pass 250 and X-ONO. Had others eg Parasound. 
Pass is a different league.
Not sure if anyone mentioned this (probably), but not every amp is a great fit for the speakers you have.  So 'best' really can not apply to any single piece of gear.

We sell Wilson, Sonus Faber, KEF, and others and have been Bryston dealer for years, but grew up on Classe' and Mark Levinson.  When we took an older PASS 250.5 in on trade and it simply bested our brand new (but burned in) Bryston 14B3 on a pair of Sonus Faber Il Cremonese's, we became a PASS dealer.  We've been pairing PASS with most Wilson's and have not found a bad combination of speakers to run with them.  We also demo all speakers over $10K with a pass amp and often sell the amp too.

I typically avoid the forums as a dealer so as to not promote ourselves,  but we really do like the PASS products (despite the fact our current order of gear will ship Feb 2019 :-(
You ask "best ever"? Perhaps for your ear, perhaps not.
I considered Passes 150 wpc integrated, and auditioned it...twice! Then I heard the Technical Brain integrated and was floored, I've owned more highend gear than I care to admit (Tube. SS. mono blocks) but for my room/speakers nothing has ever sounded like this Tech Brain integrated & phono stage It would be ideal to use a "multiple step process" before you let go of that hard earned green. Take the Pass home to your system and listen to what it sounds like in your environment, and, you will probably love it, especially if it's a rather large step up from the electronics you now own...the second step would be to return the Pass and try another amp in the same range. See how you react to a few different designs. You might be surprised, then again, you may realize the Pass is what you like...the one you pick will be the "best ever". Your speakers are the mouth piece of your system, so the "basic sound" is something that will not's all the other things that will...tonal tilt, warmth, detail, sound stage...your looking to change the heart of your system. Pass is a strong one!
You should give very serious regard to the Octave MRE 220 with the Super Black Boxes.  They will easily best the Pass Labs
I grew up with JBL Century L100s and I am very close to getting either JBL S3900 or JBL S4700.

They are not talked of much in these threads but I have a thing for JBLs :-)