I think a better question for you is... What's your goals for the stereo. Are you a basshead, or just want clean/loud, or really into 'competition' quality sound? How much space are you willing to sacrifice?
I've done the whole "SQ" thing already. My 911 had a $20,000 sound system in it....with a laser-flat EQ RTA... Not really interested in that again.
Don't want a "Boom & Sizzle" system either.... The One-Note-Drone gets old in a hurry.
I guess the best term for what I like is a "Rock-and-Roll" system. It's got SOLID low bass, but more importantly it's got an insanely punchy UPPER-BASS. (That was the reason why I was running double mids in the doors with stupid power the first time around).... The thud of the bass drum is important, but the upper harmonics of that drum note are what make it really come alive and give you that sharp punch in the chest..... a rapid double-bass attack has an immediacy that is downright fun to "experience"....it's not just a muddy, vibration with a lot of subwoofer hangover.
On the top end, I used those OD-KD tweeters (which I believe are actually a rebranded ElectroVoice tweeter) because they take a TON of abuse...they play loud without frying voicecoils, and they have a unique ability to play pretty low frequencies (for a tweeter) so you can actually cross-them over directly to the mid-bass drivers in the door (2-way) instead of trying to fit an extra midrange speaker up front somewhere to do a 3-way crossover setup.
From a SQ perpective, it will play deeply and accurately but I have no illusions that my listening environment is going to be anything but "hostile"

So it's got to be able to get up and boogie at high volumes and not lose all the low frequency information when the engine is running and the tires are howling. I had a sub-bass control knob which really helped to bring up that lost music on long highway stretches.
From a space perspective, I am going to do the same tweeter-in-the-floor setup as before and the doors are fair game for mids. I'm ditching the glass completely so I can literally seal them up tight and brace the hell out of them to make nice enclosures. For the subs, I don't want to give up much more than 1 - 1.5 cu ft per enclosure. Sealed boxes tend to be smaller than ported ones, so if I can overcome the loss of output (dB) somehow I would definitely prefer sealed.
-G