When I was first getting into car audio I cheaped out and bought an alpine cde-100 as a headunit replacement. It only has one set of rear preamp outputs and I already have an amp for my sub hooked up to them. In future I would like to get an amp for my speakers. When I eventually get an amp for speakers will I need a headunit or is there an easy work around? I don't want to lose any sound quality. Also, how important is the preamp voltage? I read that it cuts down on distortion but how much of a difference will there be between 2v & 5v?

You can get a eq of some sort ..either 1/2 din or maybe trunk mount one...or just do 3 way crossover...

No difference between 2 and 5 that is just a marketing ploy, if you wanted multiple pre-outs in the future i would just suggest upgrading to a headunit with 3 sets of preouts.

2v/5v no difference. You "can" split that rca but will lose any and all h/u control.

2v vs 5v wont matter at all, it will be the setting you will match your gain with. So if you have a 2v unit then you will just have to set your gain higher then you would with a 5v unit, both set up properly will give out the same output.

Y-splitters will help you amp other speakers, but you won't have channel separation.

I think i'll just get a new one and sell the one I have currently. I'd probably get a few extra features like hd radio or bluetooth or something. Does anyone have suggestions for headunits. My alpine is great but i'm not against trying something new. The JVC arsenals seem pretty cool.