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 find fully balanced gear sounds best used balanced, but still quite good SE...a tube pre can sound great with a SS amp...

The last couple of posts make good sense. The first one...not so much. 

Balanced pre & amp will provide 6db additional gain and reject noise. It's a clear advantage. 

Comparing balanced vs. SE pre to SE amp, both can sound good. It depends on the merits of those designs. If you ever move to a balanced amp, then you can take full advantage of balanced preamp's capabilities. There isn't a reason to reject a balanced pre now just because you are currently using a SE amp. Cheers,

Spencer

...Balanced pre & amp will provide 6db additional gain and reject noise. It's a clear advantage... 

Sometimes the added gain will show up as noise in your loudspeakers and you'll need to attenuate the gain. Balanced cables are most useful for long runs in noisy environments. There is nothing inferior about single ended connections.  

Don't put single ended and balanced cables in the same system, unless they are not differentially balanced.   All the benefits are lost if done like that.