Is there a significant gain in audio clarity going from 2.5v output to 4v output? I have a Kenwood kmr-m315bt. The Kenwood kmm-bt518hd looks exactly like the m315bt but with 4v. I am running a pn4.1000d connected to audiopipe horns, mmats 6.5`s, american bass 6.5`s in lowers and pioneer 6900 in lids. The gains are around halfway.

 

You won't be able to tell a noticeable difference at all. As long as your using good materials to hook everything up (good stranded wire and proper size for the amp, good RCA's, and good speaker wire) your in good shape.

 

2.5 to 4v a noticeable difference. 2.5 to 5 a huge difference.
Its worth it to me. Your amps will run cooler, and digital amps need all the signal they can get.

 

If you change the voltage output you will need to reset your gains on the amp(s)

 

Key word in this statement is "Amps". If you're running multiple amps then absolutely you want 4v or more from your HU. In an open environment, the difference in what you'll hear between a 2.5v HU and a 4 or 5v HU pushing only one amp is minimal at best. IMO it's not a big enough difference to rip out what you have unless you intend to add another amp later on.

 

I will be adding a pn4.520d and bridge it to the pioneers so I can have two channels from the pn4.1000d to run just the horns

 

Yep.. time to upgrade. You will love 4v vs 2.5v.