Tube Preamp --> Solid State Amp

I had an interesting conversation with my audio dealer today.  I was demoing the Focal Supra 3s and he shared his opinion/preference that he likes to choose a quality TUBE preamp (ex: McInstosh D1100) paired with a SOLID STATE amp (ex: Michi X5 integrated, McIntosh MC312 power amp etc).   Not sure if there are any schools of thought promoting or perhaps indifferent to this approach but wanted to get some thoughts?

Specifically for me, I just bought a Michi X5 (integrated amp) and am picking up some Focal Sopra 3s.  I have toyed with the idea of dropping in a tube preamp to soften/warm up the sound prior to the X5 giving it that 600w of punch @ 4Ohms but don't want to throw money away.  

I will say this, when I demoed the Focal Supra 3s, I did so on McIntosh tube preamp and McIntosh  SS Amp, and then switched immediately via a button on the McIntosh premap but using the McIntosh 275 TUBE amp.  The 275 added so much softness and warmth that the Focals almost felt muted.  It was about the best A/B comparison I've ever done. 

I know this has a lot to do with speaker pairing but was just curious anyone's thoughts on tube vs SS for separates?