Pass x250.8 vs Boulder 850 vs Spectral DMA250

The McIntosh preamp is a really weird match for any of the amps that you list. I wouldn't buy any one of them unless I could try it in the system first.

Thanks Zd452, yes of course I will try them on my system. Maybe I don't try Spectral due to it needs normally the preamp of the same brand.
I was in the path to buy a MC452 but... in the meantime... I connected a very simple class A amplifier (Audio Exklusiv P1, 35W) and I enjoy the kind of presentation. So my intention to investigate some solid state that can match my preamp.

I agree that the Spectral may not be the best match because of the Spectral preamp issue. I haven't heard a Boulder amp in years so I'm really not sure if that would work well. I will say that I think they were a little overpriced for what they give you. I don't know how different their newer models sound, though. And that leaves the Pass. Its a great amp, but if you look at how its designed, its very different compared to your Mac preamp. So much so, that I think the 2 pieces would be working against each other. For example, Mac believes in using a lot of neg feedback, where Pass doesn't use any. Pass believes in using a very simple design (very few components in the signal path). McIntosh is just the opposite. Looking at it that way, its easy to see potential conflicts. I'll use one of my systems for another example. The components are made up of several different brands: Ayre, Wadia, Aesthetix and Vandersteen. Even though I'm using 4 different brands, they work well together because they are designed by companies that think in a similar way. If I took your Mac preamp and put it in my system, it wouldn't allow the other components to sound they're best. If I took the Pass amp and put that in my system, it would be a much better match. It wouldn't take the fully balanced, 0 feedback, in phase signal coming from my Wadia and Aesthetic front end and turn it into something else. It would retain those properties as it continued to the speakers. The Mac preamp would introduce feedback to the signal. Feedback also alters phase. So just putting 1 odd component in a system can have a serious impact on SQ.

It depends on which kind of sound you prefer. They all 3 sound different. The Pass will be the most musical one in the mid freq.

You only know how it work out with your pre-amp when you connect it.

At the end it is a personal thing. It can be fun to compare, so enjoy it!!