Multiple Sized Subs Feedback Needed

OK. I'm hitting an info overload from reading so many posts. I start with the short version. I have the ski pass cut open behind rear armrest and an Alpine 1000W RMS on 2 8" JL 8w3's in ported enclosure (3rd box) with both subs and ports firing through ski pass at 50 degree from each other).

(1st enclosure sealed)
(2nd enclosure ported firing toward rear)

I'm going through an upgrade where I'll putting a FI Q12 in a sealed box firing through the ski pass. I've never heard one and I'm trying this based on so many people raving about them. First question is would it be worth it to tune the Q12 enclosure low (around 30-35 Hz) and install a custom sealed rear deck enclosure for the 2 8's to fill in between the front door component set and the Q12 (say tuned to 100-110 Hz)? Or does the Q12 have the ability to go really low and give that upper end punch? I want my bass range to be as balanced as possible. Has anyone tried anything like this?

If you do get the Q12, let me know how one sounds. I'm debating how one vs two sounds in our trunks that are very sealed off. The FI Q is a very good sub. It's a sub that has good sound quality and can get loud but not boomy. I've heard people compare them to the high-end JL subs. As for the mix match subs. I think It comes down to personal preference. Keep in mind that a sub tuned to a certain frequency when played at a higher frequency will have problems because it cannot get enough air pressure to function properly. So if you tune a box to 30 Hz you may have issues hitting notes at 80 Hz. I think that the tow 8's will get drowned with the Q in the trunk. The Q can have the ability to go low and hit hard as well as play the higher lower mid bass notes if done properly. Each car has different acoustics and each setup will need to be adjusted accordingly. I'm in the middle of redoing my system and looking at one Q or possibly two. I already have two MTX subs but I'd like more quality and power. I have some focal mids and CDT tweeters for my highs. I'm looking at getting a set of Morel components like the tempo line. In order to have a balanced sound the Morels can go down to about 50 Hz and the Q 34 ish. I'll have to set up my amps and crossovers like I do now. My mids and highs on a high-pass filter set at 50 Hz and my subs at 80 Hz. That well make a nice overlap and hopefully balanced sound. I think though I'll end up with the Morel's for my Fonts and one Q for my sub because I don't want to add a battery for extra power and I don't listen to music at high levels anymore.

Based on comments all over this board (and others), you can't go wrong with the Q12. They're comparable to JL W7 and IDMAX for loudness and SQ. It seems to be personal preference which one of the three sounds best. Since you don't listen to high levels of music, you probably would be satisfied with just one (based on what I've read). I'm going to get only one Q12 because I'm not trying to make this an SPL monster. I have another vehicle when I need that fix.

My concern is frequencies slightly above the Q12 low pass cutoff. I have a Polk 6-1/2 component set that I'll be installing like this (http://forum.e46fanatics.com/showpos...7&postcount=35) instead of those plastic adapters that come with the Polk's, but still don't know if I'll need to compensate for that 80 to 150 Hz range. In my SUV, I customized the front doors to have three 6-1/2's per door, so that range is not a problem. Basically I'm planning to use a three-way crossover setup.
Q12 - Below 80
8w3's - 80 - 150 Hz
6-1/2 components > 100 Hz

I see what you mean now. I've seen and heard three way setup's like that, but in doors. They had custom door's done with 8 inch woofers, 6 1/2, Mids and 1" tweeters. I'm not sure how the 8's would blend in though. The trunks in BMW's have a lot of sound deadening and are pretty sealed off. I had to take out my rear speakers and the ski pass to let bass in the cabin. This spring I'm adding more sound deadening to the tunk lid and floor of the trunk. Hopefully that will bounce back more bass and stop the rattles. Have you though about a sealed box for the Q and maybe some 6.5" woofers like the M6's from CDT in the rear speaker locations? I'm in the process of adjusting my new Alpine amp for my subs and they hit well in to the 80 Hz range but I have them set to not go beyond that. My problem now is that my Focal mids don't like going below 70 Hz and I'd like something that can handle more mid bass. They do sound clean and detailed above 70 Hz though.

The plan is definitely to have the Q in a sealed box firing through the ski pass, but instead of removing the rear speakers I'm planning to mount the 8's under the rear deck where the factory subs would normally go. Everyone recommends removing the rears, but I've always liked the sound of a little rear fill in a car. Its just personal preference. Even 20 years ago when I used to compete, I'd set up the car one way for comp to get higher scores and another for personal listening. The sole reason for the 8's is what you mentioned, 6-1/2 mids don't always like getting low. Obviously, I haven't customized my doors yet like JVR826 did in the post I linked to. That may do the trick but I'm skeptical until I hear it. I'm hoping to get some others to chime in on this subject.