mids, midbass

I don't think your budget is reasonable since you would need to power these mids in some way.  This requires adding a dedicated amplifier for them.  Or do you already have that covered?  Also, In my experience Diamond Audio speakers have pretty impressive midbass performance.  I'm wondering if instead of going through all the expense of adding some midbass drivers, improving the installation of the speakers you have would be the ideal solution.  How are they mounted and in what vehicle?

However if you are dead set on this, then I would suggest a pair of CSS SDX-7 midrange drivers.  I doubt you will find a better performer for any price.  Here's a link: http://www.creativesound.ca/details.php?model=SDX7  And here's a link to a tech page about the drivers the SDX-7 replaced: http://www.acousticconcepts.com.au/extremis.html

I think the best thing you can do is to improve the installation of the speakers you already have.  Your speakers are more than capable of matching up to your subwoofers, if installed correctly.  I think the world has ingrained in our heads the idea that more is always better.  However with audio, the opposite is true.  Adding a midbass driver may fix a small problem you have, but it will also add other problems.  Now you will have another set of speakers playing overlapping frequencies which will effect the sound.    To reduce this problem you are going to have to spend quite a bit of time finding the proper crossover slope and frequency, as well as the proper output level for these speakers to get them to blend correctly.  And finally you have to find the room in your vehicle for them.

Instead what I suggest doing is getting some sound dampening material and applying it to the doors outer skin, as well as the inner skin.  Make sure to cover as many holes as you can.  This should improve the midbass capabilities of the speakers. 

in my ever quest to get those wonderful mid bass frequiencies, I've done everything from multiple 6.5" drivers to having a 10" sub sitting infront of my console. like Mr. Kephart stated, "I think the world has ingrained in our heads the idea that more is always better.  However with audio, the opposite is true."

The solution to my problem is a Correctly installed system (I use the word "is" b/c i'm still working on the install) and taking some good advice from Haemphyst, Mr. Kephart and other members on the board. I've gone from 2 sets of 6.5 components with a 10" up front to a set of 6.5 tang bands, a set of 5" silver flutes, and a 1" vifa tweeter and from what I can tell so far, It's so much cleaner.

start with reinstalling what you already have. I bet you'd be suprised what a 6.5 can do when it's properly installed.

BTW... where in MS you from???? I'm in Columbus.