Powder - I've used Green Dot, Unique, Herco and Blue Dot in the 16. If I was to buy just one (for 16), I'd get Unique. That's just my preference, a lot of powders work well.
Wads - Midway and MidSouth (along with others) carry Claybusters. I got Guiliandi wads from Midway. If you've used BPI's 16 wads, you've used Guiliandis. If you want to just try the WAA16 clone before buying in quantity, an e-mail to Claybuster might get you a sample pack. Good outfit, great customer service. (No, I got no stake in the company). You're right about the unavailability of the WAA16 wads. That's why it was good for 16 shooters whan Claybuster came out with their clone. I've heard rumors of Downrange coming out with a 16 Gauge wad too, but I haven't seen any yet.
DC