MY personal rule of thumb is that if you don't NEED to use balanced I/O don't. There is additional circuitry involved to bump the level to +4 and balance it, and unless you have to use that convention you are sending your signal through unnecessary circuitry. Looking at the manuals for the Tascam 48 and 58 the HF response is actually better by 3kHz when using the -10dBv I/O on the RCA's. I don't think you need to fret using the RCA I/O unless your cable runs are over 25 feet or so and you are having noise issues as a result. The 388 is native -10dBv internally as is the 25-2. Keep it native if you can.