though i bought the v2+ as my main traveling kit w/ balanced JH13proV2 iem + silver dragon v2 wiring, today i brought my cheap(er) re-400 home from the gym today to see how they fared.
normally i use the re-400 in the gym directly from my moto XPE phone, and they are certainly adequate.
however, with the v2+ (and UAPP) in the chain, holy *$% batman!
the re-400 are much more capable and refined than i ever knew, even with single ended drive.
as an example, playing Candyman (live 1988 Dead), the intro is a slow loping sequence and with the v2+ in the chain, i heard for the first time (compared to directly driving from Moto) delicate brushes on the cymbals and light individual hits of percussion that were a mishmash of sound when driven by the android phone alone. This is in addition to the increase in detail, soundstage and bottom end.
The re-400 will never touch the jh13proV2, nor my stax 009, but the v2+ makes them a totally different beast. How much is due to the better DAC and how much due to the better output stage I really can't tell, but the improvement is obvious and well worth the cost of a v2+. very impressive and i can't wait to check out balanced mode and get a handle on the jh13proV2 & v2+ combo.