Hi Earl, glad to help. And it is a subject that I know something about!

I was using an active crossover, but now am running passive and prefer it for many reasons, not the least of which is ease of use.

The passive crossover comes after the amp, so you need only one amp. The 2 parts will be link together, but they don't really work together, that's why you can mix and match. I'll look at the design again, but I think you need only change 1 resistor value. Might put a variable resistor in there to "tune" it. That would allow you to bring the level of the horn up or down to fit your room. The crossovers will not be cheap to build, inductors are expensive, but it will serve you for years and will sound great.

As for T-amps, I have too many. Sonic impact 1 & 2, Super-T, Fenice, Virtue Audio 1 & 2, Pop Pulse, 41Hz, Sure, Trends, various Chinese, etc. They all work fine with the A5.
One problem you will have is the 16 ohm woofer. It requires a higher voltage to get 1 watt than an 8 ohm woofer. And many of the T-amps are voltage limited as they run from 12V. That will limit your peak power a bit. Like 6.5 watts peak. But that would be rather loud with the 515 anyway!