You're pretty stuck on this rear stage thing. I'm getting the feeling that you've never heard a properly designed, installed, and tuned front stage. You'd be surprised what it can sound like. You want to have as little as possible coming from behind you to achieve proper staging. Anything other than subsonic frequencies (below 80 hz) coming from behind you will pull your front stage backwards, and that's not a desirable effect.
There are a ton of problems with trying to get a front stage as loud as a sub stage that's running the kind of power you're talking about.
One is even if you get your mids loud enough to match up, you'll have so many resonance problems it'll drive you insane. Door panels LOVE to rattle.
That being said though, you can still get great midbass. A well integrated midbass will pull your substage forward so that it sounds more coming from in front of you as opposed to from behind you. That's what's meant by staging.
You're target frequency for a midbass should be 70-80 hz (with good power handling), or 60-70 hz (with moderate power handling) Under 70-80 hz, frequency generally becomes non-localized. In other words, it's hard to tell where it's coming from.
That all being said, and based on what you want from a midbass, I'd stay away from the Exclusives. They are amazing drivers, but they're not the strongest midbass performers. Once again, the CA18RNX is a stronger midbass performer, if not as detailed in the midrange. The L18RNX is a beautiful driver with amazing midbass capability, but it's top end leaves a little to be desired with a nasty breakup mode, and it's generally difficult nature. The P18RNX is the best of both worlds. (I'm stating basically drivers in the same price range)
Now if you can fit an 8" driver, and are willing to do a 3-way setup (midbass in doors, midrange in kicks, and tweeter depending on what sounds best), then the Peerless SLS 8" driver is a beast.
With a 3-way, you definitely don't need a rear stage. The SLS 8" can drop very low, and handle a good amount of power, though it doesn't need that much power to really get moving.
If you really want to do this right, and have the money to spend.
Peerless SLS 8" midbasses in doors with proper deadening and sealing. A suitable midrange driver in kicks. There are a ton to choose from. The Vifa MG14, the Vifa/Peerless TG9, a whole slew of Tang Band drivers, the Dayton RS125, etc, etc, etc. Then an appropriate tweeter, depending on the midrange you choose.
For amps, since you like Memphis, the MC300 for the midbasses, and a MC300.4 to run the midranges, and tweeters.
If it were me, SLS 8", Vifa MG14 (one of my all time favorite drivers), and the Alpine variant Vifa XT19 (because it's an awesome tweeter that only costs $14.00).
If you want a reference that what I'm talking about isn't something just out of my ***, hit up Hardhitta47 on this forum. I sold him a sub a while back and he listened to my setup. Front stages are what I do. Even though my sub stage is pretty beefy as well.
