I second Ralph's (Atmasphere)'s post.
You need equipment that supports the AES standard in order to compare balanced to RCA.-Otherwise, it is a crapshoot.
Utilizing the AES 48 standard should eliminate the effect of cables affecting sound quality.
FWIW, when I bought my Atma equipment, Ralph supplied me with a 25 foot length of XLR interconnect to go between preamp and amp (Mogami?) at a very low price. When I had an itch to scratch, I called my dealer who sold me some AQ Yukon to replace it. Long story short, I didn't notice a significant difference between the two cables. So, for me, using XLR with equipment that supports the AES standard, you don't have to pay an exorbitant price. If you use RCA, you might have to cycle through a number of cables in order to find one that sync's with your equipment-esp. if it doesn't support the AES standard.
I hope this makes sense.
Bob