I like my Peachtree Nova300 more than my new (to me) Pass XA30.5 HELP!

This is actually a common situation for people who handle a lot of gear. As a reviewer I run into such things on a continual basis. I had all kinds of interesting outcomes with the Kinki Studio EX-M1+ integrated that can operate also in dedicated preamp or amp modes. Wildly different outcomes are possible depending upon which gear, cabling, etc. are used. So, don't be shocked or horrified at the result. 

I am of the camp that would say the preamp of the Peachtree was designed particularly for use with the internal Class D, and it should not be expected that it would excel with any given other amp. 

The fact is, no one knows the outcome of a combo of gear until it is tried.  I have often had unusual combinations of gear sound better/worse than any other possible combination/component. The performance spectrum and personal preference spectrum together is VERY wide.  

There are hundreds of outcomes when mixing gear, not to mention cabling, and it is very likely that the proper preamp with the Pass amp will bring that combo to another new threshold of sound quality. I would most definitely not blame the amp. This is why I build several systems when reviewing, because you don't know the innate character/capacity of the product unless you do. 

Just the other day I put together a rig with some Pass Labs amplification on review (No, not saying which) and the Exogal Comet DAC ahead of it. Outcome, just as you describe; too warm and lacking to my satisfaction in definition. Not a great combo, although I have made stunning rigs with both of these items with very satisfactory sound. 

Then, I went through an upgrade to the Small Green Computer sonicTransporter and SONOR Signature Rendu SE systemOptique that I reviewed and use for source. BOOM, now the same combo was rich, luxurious, no longer suffering the milky, indistinct sound. Had I tried it after the upgrades were done I would think the combo to be all that - and it is, given the "new" source. 

Ergo, all components, etc. combine to yield the result. It's just not as simple as this or that component is not good, is good, etc.  

The other thing here are the recordings and one’s reaction to them.

Some systems will sound full, detailed and crisp. But some recordings will sound too cool with an edge to the treble end that becomes fatiguing. 
Some systems will sound warm, smooth and rewarding most of the time. But some recordings will sound slow, slightly blanketed and less dynamic.

So, your room, speakers, preamp, cables and front send source are going to combine with your chosen amp to deliver the sound you might enjoy with the recordings you prefer. 
A lot of variables, so YMMV...

Thanks everyone for your input.  This has been very helpful.  Tvad and Al, I did install the jumpers in the XLR inputs so that part is out of the equation.  

I'm gonna see what happens with the LTA when it comes.  Clearly the pre section in the Peachtree was designed for the power section of the Peachtree so maybe that'll change things.  It's interesting, I agree that the Pass sounds more dimensional and luxurious and less "dry" than the Peachtree but I can't trade that for all the things that the Peachtree is doing better for me at this point.  More detail, more crispness, more highs in general and a tighter more assured sound.  Maybe I'm a class D fanboy?  Jury's still out.  Thanks again everyone

Hmm. In the measurements section of Stereophile’s review of the Nova300 John Atkinson states as follows:

... all measurements of the nova300 were taken using Audio Precision’s auxiliary AUX-0025 passive low-pass filter, which eliminates noise above 200kHz that might otherwise overload the SYS2722’s input circuitry. Without the filter, there was almost 1V of ultrasonic noise present at the Peachtree’s output, with a center frequency of 472kHz.

And I would expect that 1 volt of ultrasonic noise to be considerably greater when the Nova300’s preamp section is being used in conjunction with the Pass amp, since a speaker load is not connected to the Nova in that situation.

In other words what you’ve got in that setup is a **very** powerful RFI generator located somewhere in the vicinity of the Pass amp. I’m thinking that a significant contributor to the problem may be the result of that RFI finding its way into the Pass amp, either by coupling into the power wiring or the interconnect cables or the speaker cables, or perhaps directly through the air.

Good luck. Regards,
-- Al