Open baffle/ dipole design help

[Infinity buff]

Hi, I own a pair of Infinity RSII speakers that I am in the prosess of upgrading. They have 2 10" woofers, three 5.25" mids and two ribbon tweeters per speaker. To date, I have replaced all four woofers. The uppers are Vifa's and the lower ar Dayton Hf's. Ultimately, the lowers will be connected to a pair of plate amps and will be used as powered subs. I have one connected to a 150w amp now and I soon hope to add a rythmic 350w with a Linkwitz transform tuned to 25hz (-3db).
while I await my amp, I wanted to get some ideas on upgrading the mids.
Ideally I would like to simply replace the existing drivers, but I realize I may have to modify the xover to achieve the best results. I am willing to change out caps, resisters ect, but I want to retain the original circuit boards.
The drivers ohm out at 4ohms so I think that is what I should stay with, but I am open for suggestions. Note: The Vifa's are not very efficient and I have to turn the mid volume all the way down to get them to blend and I still am not sure they are right. The Vifa's are rated at 83 db with a 2.83v input. Some one said that because they are 4 ohm they are actually only 83 db @ 2W input. Might using 8ohm in the mids help compensate for the low sensativity?
I love these speakers and hope to make them sound even better. I have been very happy with the improvements I have made to the bass units and hope I can do the same with the mids.
Any help from the experts would be appreciated as I know very little about speaker design. I need to know what drivers to buy, how to make any changes to the xovers, ect. My budget is
$300-400 or $50- 65 per driver.
I will include some pictures and a schematic of the xover, if I can figure out how to insert them!!!
Thanks.

[Infinity buff]

Another photo!

[Infinity buff]

And a Schematic......

[Infinity buff]

And a photo of the bass drivers just because.....