Hmmmmm; dilemma! I've read about a lot of excellent finds with the AT-Pro in many varied hunting environments.
You hunting fresh water or salt? From previous posts you don't get to the salt water beaches often; your wife or sometimes you use the AT-Pro. You use a CZ-5 and maybe a Tejon and had (or maybe still have) a Cibola and had a deal lined up on an Excalibur.
If you don't get to the salt water often, I'd say learn the AT-Pro and your CZ-5 and your Tejon and see what you (or your wife) like in the detectors. Keep what performs for you and then look to fill the gaps.
If you decide you get to the salt water beach enough to want a specialized detector, try the AT-pro on the wet sand and in the water. Try the CZ5 on the wet sand. See what works for you. If you think you want to add the accessories that are useful for hunting in the water, the AT-Pro should be able to detect there, but if you find you really like hunting in the water, then look at the CZ-21 or that deal you had on the Excal.
Just my humble two cents.
Cheers,
tvr