Go to Wakeside.com and check out the NVS speakers! They will also mount to the illusion x tower. The most important thing is what you want? If you what loud great sounding speakers that you can clearly hear while riding go with NVS and the correct amp with enough power to push them!
www.nvs1.net 90% of tower speakers out there look cool but have no sound reinforcement capabilities! They use car speakers, which are not designed to be heard 65' back and over wind and motor noise! They are designed for sitting inside a car or close range listening. For tower speakers you need to design or pick them like outdoor concert speakers. NVS is one of the first to do this and Skylon is catching on but I think the illusion mounts are not available (political thing between Skylon and Malibu). I will be installing the NVS addictions on my friends boat soon with Kicker amps and remote amp control unit for having complete control over what speakers are on in the boat/tower and when. If I only want the tower on, I just hit a button.