Unless you have both amps in the same room at the same time, connected to the same gear and level-matched to 0.1dB, and you can't see either amp, it's impossible to conduct a valid listening test. Also, if you check the independent, measured test results for both amps I am sure you will find they are identical in all of the parmeters that can make an audible difference.
But, as Theresa says, you believe you can hear a difference and on that basis it seems unlikely you will be satisfied with anything else but the Parasound, so just go ahead and buy it and enjoy owning and listening to it.
One thing I would say - when there IS an audible difference between amps it is invariably because one amp is being overdriven - which usually means it doesn’t have enough power for the job in hand. Personally, knowing that more power is likely the only thing that can make an audible difference (in the circs I describe), I would perhaps be wary of choosing a 125 watt amp over a 200 watt amp.
Every doubling of wattage is a 3dB increase in sound output. 3dB of additional headroom can be very useful when the system is running hard and there is a lot of dynamic range to contend with in the source. The thing is, the Onkyo is specced at 130 watts but that is almost certainly with one channel driven. The likely spec with 5 channels driven is probably about 80/90 watts. The Emo OTOH is specced at 200 watts with all channels driven, so in reality has twice or more the output of the Onk. This extra power gives you more 'headroom' so in situations where the Onk could be pushing close to its limits and starting to sound strained, the Emo will be cruising. If you usually listen at fairly low levels this may not matter much - if you like it loud it will matter more. If you want to achieve movie Reference level, it is crucial.
You have a couple of options: get the XPA and power the Left, Centre and Right channels with it and use the Onk for the surrounds (a very good option). Or get an XPA-5 and use the Onk as a prepro. Also a very good option but it will cost you more. If cash is a main factor, go with Option 1. If it isn't, go with Option 2.
If you go with the XPA 3, you won’t have a problem with the Onk powering the surrounds - they require less than the mains anyway.
They are. I have had several over the years. They sound 'warm' though simply because of the distortion inherit in tube amps. It is real easy to make a SS amp sound just like a tube amp - but nobody wants their amp acting as a tone control now we can have amps that are truly transparent to the source.
They can nowadays for sure - but was it always the case or was the warmer sound a limitation imposed by the design and components back in the day when tube amps were common?
Yes my Class A (it always amuses me when I type that ;) ) does have a 'warm' sound - I would reject it these days but I have become used to it and it suits the music I listen to. If I ever replaced it though, I would choose something more transparent for the reason you give in your last sentence. I couldn't honestly recommend that anyone buys an amp as tone control (unless they know exactly why they want to do that). The warmer sound is beguiling though and very easy to listen to, there's no denying that, and many are seduced by it.
It's possible but it should never be a material (and certainly not audible) factor in today's equipment. Back in the day, separates had several significant advantages over integrated units, but these days, with better design and better components, the differences have been pretty much eliminated.
I have an Onkyo 5509 prepro and Emotiva XPA-3/UPA-2 amps but I seriously doubt if there would be any audible differences if I just used an Onkyo 5010 AVR. I have the Emo amps because when I bought them I had very difficult to drive 4 ohm 'audiophile' speakers and they were, on occasion, too much for my then Onkyo 5007 AVR. Having bought the amps, it made sense when I wanted to upgrade from Audyssey XT in the 5007 to XT32, I chose a prepro. (I also wanted a unit that was capable of being used with Audyssey Pro, which I now use). But HST, on reflection I may have been better off buying a Denon 4311 and using it as a prepro. The amps would be 'wasted' but they'd be a nice backup if one of my external amps ever went down. The 4311 was terrific value towards the end of its life. Mind you, I got my 5509 (by importing it from Germany) for cheaper than the 4311 was at the time, so that was a bargain really anyway.
The one thing I think nobody can challenge about separates is that they look ****ing cool :)
You won't have any problems at all driving the surround channels with the Onkyo. (I am assuming you use fairly typical surround speakers and not refrigerator-sized 2 ohm specials ;) )
IMO it just comes down to how much you want to spend - there won't be any difference in SQ between your different options and the Onk is easily good enough for surround duties.
it was me...
sometimes I don't 
