If you are going to go active I would go with 16 per tower 4 sets in series of 4 in parallel giving you a 4ohm load. I would also go sealed and eq the low end up. ====/====/====/====

With the PT2 use between 8-12 per side. I use 100ufd capacitor on them for protection. 12 will put you at almost exact the same vertical as the mid line of 16, but realistically Use a 48db slope between 1800-2000hz. 6ohm load ====/====/==== or 2.6ohm ======/====== depending what amp you are using.

The easiest way to go active is to use the crown xti amps. They are slightly costly but have all of your eq and xover features built in! Or use a behringer dcx2496 which is what I am currently using.