Tubed Monos for Focal Aria 948s

I'm considering a pair of tubed monos for my Aria 948s. Given that their efficiency is at 92.5 it seems that I could swap the 130W SS monos for the warmer tube sound in the 40W range and not have any issues. Any ideas how much bass would be lost? Do I need to factor gain into the equation? Already have a tube preamp and like the way that sounds, even like the the way the SS monos sound but since the Focals are so clear my thought is that tubes would pair very well.

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@arctikdeth I'm running a pair of 180w mono blocks into them now. I would like to keep the wattage up there if possible.

@erik_squires That's exactly what I noticed too. I spread the speakers further apart and removed the toe-in which seems to have worked in my room.
If no-one's mentioned it, that speaker should be on the 4-ohm tap if using tubes. The woofer array is nominally 4 ohms- that's where you power is.
@atmasphere First I've heard of it. The amps don't have a 4 ohm option otherwise I'd give it a try
@zyphryx  A transformer-coupled tube amp without a four ohm tap??

No worries- a set of ZEROs ( can fix that. If the speaker is bi-wirable you can try putting the ZEROs just on the woofer section. 
@atmasphere Can't bi-wire these speakers and the preamp is tubed not the mono blocks. They are solid state. The whole post was about switching the mono amps from SS to tubed and what the trade-offs would be.I've added a TT into the mix recently, so I may just leave everything as is now. The sound is great right now except for minor placement tweaks