Pairing of PreAMP and Amplifier


I have reached a fairly high level of audio in my home but I am unclear as to the importance and best "rules" of matching the pre amp and amplifier objectively. I currently am have Audio Research REF-6  pre amp and a new Burmester 911 MK3 solid state amp which I bought on a whim.( I previously had a VAC 300.1A which was a wonderful tube amp.) I was thinking that I should try an Audio Research REF160S- monblocks are a bit much for my room.
 I do enjoy buying and selling audio but I am also getting tired of all the stresses of same. I am trying hard to find the BEST combination and not sure if my current pairing is as good as I could appreciate.  I have recently acquired Avalon ISIS speakers...My source is CD - currently Audio Research CD9 but considering Esoteric.   
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The Burmester amplifier is said in various places (here, for example) to have a balanced input impedance of only 1.88K , while like most ARC line stages and preamps the Ref-6 has a recommended minimum load impedance of 20K. So if you are using balanced interconnections between the two components you are certainly not hearing them anywhere near their best.

When unbalanced interconnections are used, though, via the adapters the amp is supplied with, the input impedance is said to be 22.9K. So if you already haven’t I would definitely try connecting in that manner before proceeding any further.

Good luck. Regards,
-- Al
That was extremely helpful ...thank you 
Interestingly, I learned that the input impedance of the Burmeister is actually double the RCA number and exceeds 45 K.  Unfortunately printed material was distributed, which Burmeister has acknowledged is incorrect!! Very verified  that the balanced input is of course superior in my situation. 
Thanks! Good to know. I recall that incorrect spec misled another member in a thread here a few years ago, although I don’t recall what the upshot was in his situation.

Regards,
-- Al