Tube amp/ preamp advice

35wpc seems a bit low to me in that large space

McIntosh MC275 would give you 2 x 75wpc with 4/8/16 ohm taps (what impedance are your LaScala?

future option for a second for a pair of 150 wpc mono blocks, (in case you change to less efficient speakers some day) but no 16 ohms, bridged options become 2,4,8 ohm taps

MC275 listed here, asking $2,900

MC275 LE 50th anniversary limited edition 

Tube Preamp:

Staying vintage, leaves you plenty to get a McIntosh Tube Tuner/Preamp, I love my MX110z, if it died, I would replace it without hesitation, one of the reasons is it's wonderful sounding MM Phono Inputs 1 and 2. Only a SUT needed to use LOMC, retain sound of the MX110z's phono.

I had Audio Classics overhaul my MX110z, including all new gold plated  RCA Jacks

MX110z, was serviced by Richard Modafferi at Audio Classics

https://www.audioclassics.com/mods

I’d stay away from flea powered amps.  800 sq.ft.is still a good size area.  You’ll need power particularly if you are going to crank it. Years ago, I had a friend who converted his garage into a party room.  About same size as your loft.  He had 4 Klipsch horn’s, one in each corner, powered by 2 large Mac SS amps, 400w-500w each.  He lived on a cul-de-sac and when he cranked it we would open the overhead doors, go outside and sit in the middle of the cul-de-sac circle to listen lol.

Thank you for all of your advice. I am very new to the tube world. I have always been smitten by the 275, I'll do some research on them. Preferably, I would like to have a preamp that is solely an amp, and no tuner integrated. Now that we've narrowed it down to a 275, can you make any recommendations for that? 

You need to actually hear your candidate amplifiers.  Tube amps are WAY more variable in sound than high quality solid state amps.  I personally don’t like the MC 275 amp, in particular, anything made in the past 25 years or so.  They sound so dead to me.  Obviously, a lot of others like them, do it is a personal preference.  

For the money you are budgeting, you should consider an integrated amp.  With some designs of amps, an integrated amp is essentially the same as the power amp with added input jacks, a source selector and a volume control—it costs relatively little to turn the amp into an integrated amp and the buyer gets some of the savings.  It would help to know what features you need in your amp, like, remote control, balance control etc.