I'm with Chris J on all this. It's more execution than type and common mode rejection is just not a significant issue in home kit. Great for long mic or instrument runs with all kinds of spurious stuff around. For balanced to be as good as single ended it needs the inverse amp to not only measure as well but to be an exact inverted duplicate in the way it behaves dynamically. When you get into top quality designs where transistors are trace matched for top performance, it just gets that much harder unless there's some really cool distortion cancelling going on like feed forward etc.
All that said we're not in super high end territory so what your ears tell you is the better amp is the better amp and Ray makes some of those.
To the OP. If you've got a cheap stereo amp now, buy another and use them one channel each with the sources' up and down phase positives in separate channels of a single amp and the earth to the common input ground. Output would be the two positives of an amp to the + and - of one channel's leads. Ignore the ground. A bridged amp is a balanced amp. Output impedance will double, voltage swing will double and power quadruple. Check bridging an amp if you want to try.
Edited by goodvibes - 2/15/14 at 5:52pm