HT and 2 channel in same room? 1 or 2 systems?

This is an excellent question and very appropriate for me.  I was very excited this morning to read the responses and potential solutions offered by the Gon’ers as I am currently building and trying to figure out the same issue.  IMO with enough research and asking enough questions to the right people, there is always a solution even if it’s a compromise.  But life is all about compromises that you can be happy with. For the OP, I believe the solution is a preamp with HT bypass and sub pass through and is neutral enough to not color the tube amp.  I would keep the tube with the LaScala’s.  I’ve heard them in a room your size and they are one of the top 5-10 speakers I would choose to try in that room.  For the rest of your system, or systems, of integrating subs across HT and 2 channel, here is what I intend to do.

In a mixed use dedicated room,  14x22 fully sound controlled to the best of my ability, I have prewired for 7.4.4 + 2channel mains and riser platform acting as bass trap/ theater seat riser.  I have acquired almost all of the following gear.  I lack the Pre with HT bypass and the DIY subs.  If I am overlooking something obvious, please let me know why this won’t work or you feel that the compromises seem more than it’s worth.  Also, this is my critical listening room, so the compromises need to be minimal.  
Denon x4200h AVR with Rotel amps driving LCR, SS, RS and Atmos. Sub out to miniDSP for passive DIY subs at side and back of room.  Front wide pre out to 2 channel Preamp with 2.1 HT Bypass to amp driving another set of LR as 2 channel mains and  acting as Front Wides when in HT mode.  LFE from AVR also sent to .1 on Preamp bypass into REL subs in front of room.  REL subs also wired high level from 2 channel amp for 2 channel listening.  Video sources sent to AVR and streamer sent to 2 channel Pre.  Room treatments are next but I obviously need to have the system setup and REW before I start on that.  The one issue I haven’t solved is the fairly large projector screen as a reflector between my mains.  My only option may be to use a curtain to pull over the screen for critical 2 channel listening but one thing at a time.  My room is not huge so compromises of speaker placement is a very big concern of mine, but it is what it is and a viable solution will present itself with enough trial and error and enough equipment in and out.  Hopefully, responses to this will help the OP as well as me.  

@kota1 

Thank you for the suggestions, especially the upgrade for Audyssey.  I have had that Denon AVR for a couple years but have never plugged it in.  I guess I didn't realize that it would take me a year to finish my basement / theater room.  I have a JVC projector sitting in storage that I've never plugged in either.  Same goes for the Oppo 103d BD.  Hopefully all this works as planned when I finally get it hooked up in a few weeks.  Fingers crossed.

I think the OP had another concern about how to set up subs in a dual use situation which is my concern also.  It was said earlier that using a sub that has dual inputs would work for this use case.  In my case, I found REL and Sumiko to be appropriate for this use case for 2 channel as well as HT.  Not sure how well they will work for this but it is their intended use by design.  I am not a big bass head, but do require it in my music and movies as I can easily hear the difference that subs bring to the stage.  My goal will be subwoofer integration into 2 channel and ultra low for HT.  I'm not sure about the latter with the Sumiko S-10's but I intend to DIY some 18's or 21's to help out with that and hopefully pick up the lower 20hz or slightly lower if I can get there.  I have heard that on a concrete slab, getting below 20hz is wishful thinking for me.  I'll give it my best shot.  Thanks to everyone for the information that has been put out that helps me and sorry to the OP if I may have hijacked some of your thread.  I believe we are both searching for the same answer to the same question.  Good luck to you.

@speed121