get a HU with custom fiber glass/racks etc installed to the side of your car, within glove box, under the seat (and pull out when you need to control it, or just use remote) or whatever fancy place you can squeeze into other than the space you want to put your fancy meters where the hu originally sits.

=edit=
yes i realize this thread title, however having a non HU (eg: getting a PMP and then line/aux into an amp/converter) is just too much of a hassle than having an actual HU.

the only alternative to HU is a decent android device with line/aux out to connect to the amp/converter. and that's it. where you want to place the PMP/android/iphone or pod devices etc is your call. however you'll face similar issues, and i believe there's no convenient remote to those devices and you have to plug/unplug them all the time, and may or may not have radio functions.

This post has been edited by Quazacolt: Jan 21 2013, 06:14 PM