Hey, by a total stroke of luck I determined what those opamps are:
"E53" is short form for "OPA 2353", dual, single supply (+5V), rail to rail, CMOS opamp.
They claim to have pretty good SNR and low noise. I wonder why they use CMOS though. Usually bipolar or FETs are used in audio opamps. The only thing I can think of is to be able to run at 5V.
So, if I had to guess I say this unit runs at 5V completely, both analog and digital stages. And I would also guess that mods could not help much. It is *very* hard to run good audio at 5V. It would be much nicer if the unit stepped up to something like +/- 9 or even +/- 15V though...
Richard