Hybrid Audio Imagines have great midbass. They're not just loud but also quite delicate. They have 12mm peak-to-peak xmax excursion. My primary concern with them is to stop door panel from rattling. They can easily be high passed at [email protected]
(that's the manual recommendation) without sounding harsh or sloppy. HAT Unity uses the same woofer but with a more robust passive crossover if you need it. These are one of the best if not the best $350 speakers. For higher price you can also look into Focal Polyglass 165 V30 or Hybrid Audio Clarus (even beefier driver). A forum regular compared HAT Imagine and C5. There is a review in the archives. According to that review, they're about the same level, with a lot of people split on which one is the best. Back then HAT Imagine did have the advantage of costing just $250 or less when on sale. It looks like the new Imagine V2 version is priced at $300. I have no idea what has changed since the original was released. I have the original version in bi-amp setup. In passive setup Unity should probably be better.
For the lower budget, I have heard that people who tested the new JBL MS speakers liked them a lot too, and considered them very good value for that price. Another speaker set with good midbass driver is Massive Audio CK6. These actually have stronger midbass than Imagines according to reviews while still keeping the mounting depth at reasonable 2.75 inches.
Having said that, I don't think that 8 inch sub will deliver less mid-bass than a bigger one. In the midbass region, the excursion requirement is lower than in deep bass, so the small sub should be able to keep up. Also most bigger subwoofers do not play well or loud in the mid-bass region to begin with. I have experimented a lot and decided 50-60Hz low pass frequency works best for most 12 inch subs as they get too recessed, or too sloppy or too punchy above that. The frequency region where the 8 inch subwoofer will run into trouble is the body massaging deep bass. You can get more out of 8inch in a specially tuned vented box, but most still need a tuning frequency too high to play the deepest bass.