I use an Audax TW025A0 or TW025A12. I like and use the A12 best. Better voiced for Jazz, Classical and home theater. The A0 is less expensive and better voiced for Rock.

The Pioneer AHE60-51F has worked well for me too and a great deal at 9.00.

You can use a simple crossover to protect the tweeter and still allow the woofer to roll off with the coil. I'm using a little steeper crossover than that right now that I'm very happy with.

If I'm not mistaken, I think the Pi alignment is pertinent to the woofer and tuning of the cabinet for the woofer.

Bill