If there's only one preout, chances are it's an older unit rated at 2v out.. Most likely you're getting even less than that.
An EQ/x-over will help balance things out and drive the signal, but if you're gonna be dropping some money on a system, you'll want a better headunit with more room for expansion.
Of course Alpine is a big name, but I couldn't begin to start listing model numbers for recommendation because I don't have a clue.
Eclipse has some units with 8v preouts, but you'd be paying for that 'feature'.. I think they're the only ones that offer it. The sound-quality is said to be on par or better than Alpine.. The only difference might be that Eclipse offers cleaner sound, while Alpine offers more features and goodies, but both offer great decks in their own right.
I hear some good reviews on the SQ out of the Nakamichi line of headunits, but have never heard any personally.
I'll be running a midline panasonic (switching from pioneer) in the near future. But they seem to have a good line of decks to choose from too.
I know this got long, but I felt like talking about headunits.
You're probably not even in the market for a new one. But you will be sooner or later.
Stay away from kenwood, fosgate, sony, or any of those other "budget brands" you might find at Best Buy. They offer some decent units, but you'll be paying $100+ too much. Do some research, and you can find some quality decks online at a reasonable price, with a warranty.
End. Sorry.
