'No highs, no lows, it must be BOSE'
I can understand where you're coming from regarding the compatibility, not the best. But a head unit change will result in a change in required for everything else......
As for the sound, how have you got it set up? For a vaguely decent sound, you'll need to fade it forwards a couple to get rid of the confusion from the rear mounted speakers. It also adds a slight definition to the bass. As for the 'one 10 isn't enough, I need 2 12's', I couldn't disagree more.
A decent 10" sub would give you more useable bass hands down. 12" subs do not have the snappiness you'd need for general listening unless you're putting mid bass drivers in the front doors? My last competition car had one 10" sub strapped to a proper amp and that could get all the way down to sub-sonic levels and still snap like mad on dance tracks. Please don't add a person's worth of weight with 2 12" subs, buy a decent 10 and spend the rest on proper install and finishing. Plus to do the 12's justice you'd need two amps.
And then you'll need to spend a lot of time listening to set it up, if music is your bag. Got plenty of test CD's if you're interested, so you can see what it should be doing. Depends how far you want to go!