Your amp is not differentially balanced and therefore you will hear no improvement. Balanced connections actually have 2 separate circuits ...one for the plus and one for the minus signal. What you have is XLR connections that are there for bragging rights. ..that’s not denigrating your amp...it probably sounds fine. If it were to have true balanced connections, the unit would cost twice as much.Stringreen, I suspect that you meant to refer to the OPs Marantz 8802A, which is a "network audio/video surround processor/pre-amp/tuner," not to the amp. The model of the OP’s Krell amps has not been stated, and some Krell power amps are fully balanced.
Also, it can be inferred from the specs of the Marantz 8802A that it does in fact provide true balanced **connections**, since the specs indicate a "rated output" that is twice as great for the XLR outputs as for the RCA outputs. What it presumably does not have is a balanced internal signal path, which IMO has no relevance to the questions that are being discussed. And as we’ve discussed in past threads balanced connections between components having unbalanced internal signal paths (and, again, the Krell amps might very well be fully balanced) IMO may sound either better than, worse than, or similar to unbalanced connections, depending on the specific designs.
Regards,
-- Al