Would switching from RCA-RCA to XLR-RCA from Preamp to Amp result in higher gain

Need some advice and knowledge here.  My preamplifier (Rogue RP-7) has both XLR and RCA out--two pairs each.  My mono bloc amplifiers (Odyssey Kismets in Stratos cases) have only RCA inputs.  When I switched from a power amp with XLR inputs to my current amplifiers, I noticed that I have to turn the volume up higher to achieve the same sound levels, about 20-25 points higher per the preamplifier screen indicator level.  My cable runs to my mono bloc amplifiers are about six feet and 15 feet.

 My first reaction was to sell the Odyssey amps and go with either Van Alstine M225s or Schiit Tyrs, but the Odyssey Kismet's sound so wonderful I don't want to let them go.  I suppose another alternative would be to have Klaus build another set of these amps with XLR outputs, although  the amps are not balanced internally and there would some loss involved.  The other option is to buy XLR to RCA interconnects, which is what I am asking about.

My questions are:

1) Would switching to a pair of decent quality XLR to RCA cables take advantage of the (usually) higher voltage of the preamplifier's XLR outputs vs the RCA outputs and let me reduce the volume level on my preamp?    

2) Are there any downsides to having to turn the preamp level up so high with the RCA interconnects?  I don't really hear any increased background noise at the higher preamp level.

3) Should I expect any other downsides by using hybrid XLR/RCA cables?  

Manyi thanks for your responses.