I've built an RA-1 clone. At first I was very impressed with the large sound stage, but after a while I found out that this is a coloration. It's probably due to a relative high battery impedance. The midpoint of the batteries is used as virtual ground. The impedance with NiMh's is 2 - 3 Ohms, and the output impedance of an opamp is something like 0.1 Ohm in the audio band.
The ground is as important as left and right channel, and should be as good. I'm not sure it has to be separated from output ground like in Mini3, PPA, LISAIII etc, but it has to be good. TLE2426 doesn't sound very good, but can be used as a rail splitter in front of a good opamp. In this position it doesn't affect the sound.
I like the combination of AD8599 as L/R and AD825 as ground, and they are cheap. Very neutral, just a slight JFET coloration i.e. a bit grainy. I don't think those old JRC opamps used in RA-1 is on par with the newer ones.
Mini3 is a convenient way of getting a top portable amp, but it won't give you the satisfaction of having built your own amp