Focal 1028+Mcintosh MC275

You absolutely cannot go wrong with the MC275. It has plenty of power and it is so smooth. 

The dealer I purchased my MC275 and La Scala speakers from is also a Focal dealer. They were primarily using McIntosh SS amps with tube Pre-amps all the Focal speakers. I did see a MC275 hooked up to a pair of Focals, but unfortunately didn't get to hear the combination. 

I do admit that I was probably too distracted staring at the pair of Sonus Faber SE speakers in the next room. It's not often I get to see a pair of $250,000 speakers. He did let me listen to a pair of Sonus Faber Aida's though. That was really really nice. 

Cheers!

I have a McIntosh MC452 driving a pair of Focal Sopra No2's and that combination works really well.  I've auditioned my speakers with other amplifiers and have found too many of them cause "edginess" with that Focal tweeter, but not the McIntosh.  If anything, the MC275 tube amp should pair as well, if not better than the amp I own.

I'd say "go for it"!

Sterophile measured and reviewed the Electra 1037, so the generation prior and the larger speaker. I’m guessing the measurements are similar but don’t know. Anyway John states that they will sounds tipped up when using tube amps. https://www.stereophile.com/content/focal-electra-1037-be-loudspeaker-measurements

So just be careful you don’t get the opposite effect you are looking for. 

Mac C8 tube pre might be safer with a solid state amp. $4500 I think. 

https://www.mcintoshlabs.com/products/preamplifiers/C8

The 275 is a superb amp.  It will drive anything. It’s super smooth and has plenary of bottom end weight.  It’s also not as colored as other amps for this period.  (I’m thinking marantz 8, which is warmer on the top)
I’ve never heard a bad Focal speaker.  You should be just fine.  They should sound wonderful together.