Anybody use a single ended component with one that is balanced?

This is about the noise floor.  What you lose when you go from a fully balanced Preamp to a SE amp is common mode noise rejection.  The signal is sent normally and inverted in a balanced unit.  Any commonality between those two signals is rejected which is why balanced gear is so quiet.  It is also why it is so expensive because the entire circuit is doubled.  
 

With the ARC you are paying a lot for something you aren’t taking advantage of and it won’t be at its very best.  It is up to you if it is worth the added cost.  

I'm using an Atma-sphere S-30 which is fully balanced with a single-ended Audio Note preamp. IMO, choice of interconnects will enhance the synergy. Very pleased with the sound.

XLR and RCA both are OK, usually XLR give you 3d,spacious sound body.

RCA give you the taste, some time some one said mellow sound.

It’s all depends of your selection.

Some time I will use RCA to XLR cable in small space for vocal jazz, and feel very good.

It also depend on the speaker cable, and pre

I always think a tube pre is not a good choice for SS amp.

If it is a Tube pre +Tube Power or SS pre + SS power or SS pre +Tube power will be better result for sure.

some pass labs fans are looking for first watt model which is all RCA and put pass labs XLR model aside,as they are here to  chase the taste.