Got the car back this weekend. Went with the free air suggestion and installed two 10" free air Orion subs in the back firing through the stock 8" opennings. Subs and front Focal speakers are being powered by an Orion amp (65 watts to the Focals and 130 watts to the subs)with the subs at 2 ohms. Installer went with the converter and kept the stock head unit. Mids in the rear of front door remained stock.
Biggest change is the volume especially the bass response. System is VERY loud but I find myself turning down the volume after a short while...it seems to be too bright and the bass seems too much at times; however, if I do turn down the bass, the mid bass disappears dramatically. If I turn the treble down, seems that the vocals drop off.
According to the installer, the Focals take about a week to break in and I should notice an improvement in the vocals and a little in the mid bass. One suggestion he did have is to put in an EQ and tweak the sound somewhat. I have a feeling however that the short falls are mainly due to the converter.
All in all the system sounds great and is much better than stock. I did turn the fader a little towards the stock rear mids in the front door and it did help to take out some of the brightness.

One strange thing, I noticed that the bass response is much greater if you crack the windows of the car....not sure why.
Also, am noticing some vibration at particular bass notes but not much.

One final thing. The automatic volume control is very apparent now. Installer says there is no way to disable it.