As for your statement that I always ask about drivers, indeed a good preference is helpful in narrowing things down but you are on a budget, doing a three way, and surely have goals that seem well thought out. As always the install (including tuning) is more important than the driver choice so as long as they have the capability to blend together you are fine.
So yes, personally I would spend your money first on the mid, second on the beefiest XBL midbass you can get and then forego spending much on the tweeter.