I have small canals also.. so had the same issue..
The A4's replaced the Qi's..
I honestly can't discern much difference between my Qi's and A8's.. except for the "air" and "sound stage" the ADEL tech produces. The ADEL's definitely reduce (or eliminate) any ear fatigue with gig use.. I used the REV33 with my Qi's, but have found no need with the A8's.
I highly recommend an minimum of 3 drivers if you play bass - like you have now - so that would be A3's at a minimum.
A4's will give you TWO LF drivers - more bass, tweak to taste.
You might call 1964 and talk to Alex about your concerns over which model to go with.. I have found (between both sets I own) that the EQ curve shown on their site is fairly accurate.
FWIW - our singer has A12's and absolutely loves them.. he can get lots of talent in his ears