[Darren]

You could definitely do two on one side and two on the other, perfectly adequate. I'd start with one on each side but cut the holes for the other two and put covers over them. Two of the SS drivers will basically be like adding 4 or more daytons. I think you'd be very pleased and would have room for future expandability. Your Towers should keep up just fine if you calibrate your system correctly. My guess is you have your bass too hot trying to compensate for the lack of output from one single moderate excursion driver which is why it's bottoming sometimes. Going with two SS RL-P15's will open your eyes dramatically!

I started with 2 experimental moderate excursion drivers and was impressed, not bad I thought. I added two more and got better low end extension. Wow! I was happy but wanted more SPL so I returned the experimental drivers I was testing and ordered 4 RL-P 15" drivers. HUGE improvement but of course you pay for it. The other drivers met my expectations but I wanted more than they could provide.

If I were you and could afford to go with two SS RL-P15's I'd go that route and leave room for two more for the future although I'm sure you'll be happy with two.

My system may be considered overkill by some in my room. I can easily hit 120db with just the subwoofer and no mains. I love knowing I can do that but what is more important is that I get wonderful bass at normal listening levels without strain... my amp sometimes strains at higher volumes but thats a different issue as the drivers haven't even broken in fully yet.