My advice is to go ahead and replace the entire system. It can be done on a tight budget. I sourced JBL GTO components on Amazon for under 75.00, a Precision Power Phantom 900.4 4 ch class D amp (sonicelectronix has them currently for 169.99 with free shipping). The amp is under the passenger seat - its a close fit but works well. and SWS earthquake shallow mount 6.5 subs for the rear. they fit into the factory baskets with a little modification. If they are still available the pair is about 100.00. All this pulled together nicely with the Blaupunkt HU that was in my car when I bought it. Doing the install work myself the amp and speaker upgrades was less than 500.00 and I am very pleased with the result.

I completely understand your frustration with this, it took me several months to figure something out that fit my budget. The only thing I was not too thrilled with on my install is that I miscalculated that the amp would fit into the stock location. I am sure there is something suitable out there that will fit, if you go that route.

I am not too far from you ( in Greensboro) if you would like to meet up to see and hear my setup.