XLR adaptor advice

you would be wasting your money. The only way to fly is with ALL differentially (true) balanced equipment

 Once you install an unbalanced interconnect, the pathway is no longer balanced. An RCA to XLR adapter will not be converted to a balanced signal.

A IsoMax transformer will accept RCA input and convert it to balanced. The outputs are XLR. 
https://www.cs1.net/products/jensen_transformers/PO-2RX.htm

There is nothing to gain by using unbalanced cables in an otherwise balanced system, and potentially lots to lose.

Don’t do it. Dan would be horrified. Great balanced cables can be had here for 50%+ off. You would always be questioning yourself.
Just take a look at AQ Wild Blue Yonder and Wm Low Signature as an example. Being blown out in anticipation of new models coming out. The obvious point is that you can purchase AQ’s best silver cables at huge discounts. I strongly doubt that after 40 years a cable breakthrough will occur. This is just one example of many. FWIW

Any advice/comment on using XLR/RCA adaptors?

Don't. The others are right. XLR by the way are designed with professional use in mind and so incorporate all sorts of features that are of little to no use in the home. Don't put legs on a snake.

From the preamp XLR out to a pair of Krell Evo 600 mono amps

To add to the good comments the others have provided, most (but not all) XLR-to-RCA adapters short pin 3 (one of the two signal pins) to pin 1 (ground). Depending on the specific design of the component, shorting pin 3 of an XLR output to pin 1 may have the following possible results:

1) Damage to the component, eventually if not sooner.
2) No damage to the component, and reasonable sonic results.
3) No damage to the component, but severe buzzing or other sonic anomalies. See this thread for example.

Also, with some designs whose output signals on pins 2 and 3 are floating relative to ground, hum and/or improper operation may result if pin 3 is NOT grounded.

As others have said, don’t do it. Certainly when it comes to XLR outputs, unless a very specific ok is obtained from the designer/manufacturer and you know whether or not the adapter grounds pin 3.

Regards,
-- Al

Thanks all for reaffirming my intuition...I have mainly Stealth cables in my system and was a bit tempted to get these to maintain that consistency, but not at the expense of SQ...

there are some XLR Sakras available here, at substantially more than the deal I was offered on the RCAs, and I’ll take a run at those.

cheers,

Mitch

What about having someone re-terminate the cables?