How many of each speaker did you run before?
mids and highs aren't like subs. When you add more subs and double up the box, you get similar response, just more volume. Mids and highs interfere with each other due to the higher frequencies shorter wavelengths. Meaning if one set sounds how you want, warm, good balance overall, adding 6 sets wont' sound just same, but louder. The mids will fight each other and youll have a ragged response compared to one set, and it won't be as loud as expected.
Selenium makes decent stuff, but there are other pro audio companies out there that make nicer stuff. If you want a quality sound like you had with the focals, but with the sheer output of pro audio gear, you just need good pro audio gear.
Personal suggestion would be to get some horns from ES audio. If you PM me I can give you his email address. You mount them under the dash and they are built to fire the sound up, they will sound like they are on the dash when crossed over properly.
From there if your trying to fit everything into the door I'd do a set of 10inch midbasses in the lower door and then do a set of 8inch midranges in the upper door panel.
With the right power backing it all up (250-500 for the midbass 100-250 for the midrange and 10-20 for the horns, it'll keep up with a 150-160db substage no sweat.
I'd get a processor to cross this all over to make it easy.
Something like the mini dsp doesn't cost a whole lot for what it does.
If your serious about it, I can get more specific with my midrange and midbass suggestions.
Anyways if done properly, this setup will sound clean and even like a set of normal components, but get as loud as a bunch of cheap PA mids in a door will. It'll sound louder to the ear though, due to being able to really keep everything in phase.