I wouldn't get hung up on 4v if the DAC on the radio is low quality. I've used 2V units that smoke 4v budget radios when it comes to sound quality.
Just FYI
The DAC On that 318 is 24 bit according to Crutchfield
Its a new model this year. So maybe thats the difference
Specs seem up to par with the CD versions like the 765
As stated here 4.0 volts 13 band EQ HPF and LPF with good options.
I'm a complete audio novice here, but had heard a Dragonfly system at a rally and thought it sounded great with good power. Wanted to see if you more knowledgeable folks could render an opinion. Thanks.