Switching from solid state to tubes

The front channels are the dominant channels- its not silly at all to use tubes for that. Have you tried a tube amp on your Sonus Fabers? I suspect you will want to use the 4 ohm taps.

The problem you have is that a good tube amp that sounds musical and makes 200 watts is pricey. But you may find that you don't need as much power due to the way tubes present music (which is a topic for another thread I suspect). Your processor should have no problems working with a tube amp or amps, even if mixed with solid state.

I would see if I could borrow a tube amp with maybe 60 watts or so and see how it fares- if you need more power, how it sounds, that sort of thing.

Nothign wrong with the idea, but the dynamic range and power requirements for film are a lot more than for music.

The biggest issue you would face is the disparity between your mains and everything else when listening to movies. You could alleviate this somewhat by setting the L/R speakers to "small" and routing all bass through a sub.

tube pre-amp with SS amp(s)

A VAC PA 100 offers 100 watts with taps for 2,4, and 8ohms.  Used, should be around 2k.  Sound is adaptable via choice of input and driver tubes.  It doesn't run very hot either which is a bonus, not much more than a solid state amp.  You can do better for a lot more money, but with that said I kept the PA 100 and sold the 10k plus VAC Phi 110.  All in all a well built workman like amp that offers a lot of tube magic and flexibility for the money.  
It also doesn't go up in smoke like an ARC amp when a tube goes south.  Single ended inputs only.

Theater definitely seems like the afterthought here.  To have really good sounding theater you need the LCR all the same speakers and same amps.  You could go with a smaller Sonus center that is voiced the same. 
But, your post here is for tube amps.  If you go with a 2 channel tube amp, you will further hurt the theater sound.  As long as you are aware of this shortcoming.
My solution should be cheaper than the rest:  Use your Bottlehead as strictly 2 channel with the Sonus Fabers since you love the sound.  Buy 2 more Emotivas for your right and left for theater.  The Anthem is a beautiful piece and can easily run 2 systems for you in varying ways.  (just make sure it can pass the analogue signal to zone 2).

Good advice here on testing to see how much power is needed, and as well, alternatively keeping Flicks and mucic separate if a tube amp for the mains is desired.

Based purely on content of the two formats, music and films, my question on this maneuver is why fix it if it ain’t broke, with respect to HT?

The proposal for using a tube amp to run the mains, depends on the Anthem’s ability to pass ALL signals digital or analog to a secondary zone. Most all procs will pass analog but not digital to zones other than the main one.

If your streaming is analog prior to the Anthem, you are in a less complicated scenario.

Regardless, if you proceed with throwing in a tube amp, merely reconfiguring the mains speaker cables from what ever amp to the Tube amp and perhaps a touch of altering the levels on the Anthem is all that ot be necessary for tube amp enjoyment. This is, of course with the caveat you have a tube amp capable or maybe better said, compatible with the SF speakers needs.

True too, you may find as Atma said, you might not need all 200w the HT amp is developing, to satisfy your speakers needs. 60w glass amp is as good a place to start as any, albeit there may be more contestants up around 75 to 100 in push pull affairs available. So, hide and watch the listings for what’s what in tube power amps and costs, or dive right on in.

Good luck.

I ran my home theatre for awhile with my main system tube amp (CJ Premier 11a, 70 wpc) and it runs my 4 ohm 92 dB efficient speakers with no problem, but I eventually decided that I didn't want to use up hard to replace tubes with video so added another power amp for video only.

You need to either swap the speaker cables over when going from one form of entertainment to the other or get a switching box that handles 4 channels back and forth between two power amps.

Thank you all for your input! I eventually got the Bottlehead Kaiju into my system do drive the mains and even with only 8watt/channel it got plenty loud and still crystal clear for music. Unfortunately, even after tinkering with the levels on the Anthem, it still didn't have the right dynamics for movies. So right now I've got it running through Zone 2 on the Anthem for music only, and movies are still through SS. 

Have you considered a tube hybrid?

I have not, I was assuming (maybe incorrectly...) that the combination of tube pre and SS amp - as was previously suggested - would be superior. What would be the pros and cons of a hybrid? 

I have a Rogue RP-5 tube pre with a SS Nuforce amp. I like the combination. However, from what I've read, The Rogue pre does not sound like a Tube pre in the traditional sense. Much more modern sounding. I do say that the mids and highs seem much more silky (with stock JJ tubes) than the previous Peachtree Nova Pre. 

Butler Audio makes a 5 channel hybrid tube input solid state output amp  $3k

Yep, hybrid might be the way to go.

Sonus Faber Olympica II

There are no impedance /phase graphs done on these yet. But Sonus Faber rates them at 4ohm nominal, which means they could even dip down to 2ohms. It seems they need an amp with a bit of current judging by this  Sonus Faber statement in the HiFi Choice review.   

HiFi Choice:
Sonus Faber Quoted "Suggested amplifier power is 50W to 250W with a nominal impedance of 4ohms a good, strong solid-state amplifier is needed." 

Cheers George