Soooo disappointing.
So you want to use in home theatre mode.  Get ready to pay up to operate.   The tubes stay on and when family uses system 10 plus hrs a day for tv and videos, the tubes burn away.  Most of the 8 tubes have life of 4000 hrs and cost $150 per tube to replace.  Over 5 years operating costs could approach $5000 or more.  And this excludes wasteful elec costs of $100 to $200 per year for bulbs running without being used.   Sooooo disappointing.

I called audio research and they confirmed all this.  Further, they lacked any sensitivity to theses issues.  Seemed kinda arrogant.  

Sooooo disappointing.
ARC has done their job and produced an extremely high quality stereo component for "stereo use". Being  as nice as they are they also gave you an option  for the home theatre bypass option to use I would guess once in while for the odd movie or sporting event. The problem here is that you want to use it all the time like a receiver.. 
It wasn't built for that..
You gotta make a choice here --  suk it up and keep buying tubes or get another room for the system or like another poster here mentioned get a nice sound bar...

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You can use tubes you buy elsewhere.  But, be aware, that will void the warranty. If a tube burns down, ARC will often have other problems, like resistors that burn too.  You have to send it back for service, and you will pay unless you got the tubes from them.  In some cases even if you did buy tubes from them.

By the way, look at Primaluna instead.  None of the problems you bring up, sound quality is very nearly as good, and the cost is less than half.  And, with their auto-bias functionality, you can buy tubes anywhere, they don't have to be matched, and all will work perfectly!  

I'm not affiliated with either company or the audio industry.  But, I read a lot, and I'm very happy with my Primaluna HP Integrated... for which I've never had a tube failure.  Owned 8 years.
I much prefer the sound of PrimaLuna compared to ARC, but that is just me.  I heard the Prima Luna HP mono blocks and they were quite special. I find ARC sound to be a little threadbare.