FWIW, I own Rythmiks and believe they are very good. I used to have REL Storm, and don't regret the change one bit. Rythmiks are very tight and I have them in a sealed cabinet, plus their servo seems to work really well. They also are very flexible setup-wise.
Are JL Fantom better? Most likely, as you would expect given the price difference. But two Rythmiks is better than one JL in my opinion.
I tried them with the full range speakers running full range and the subs supplementing the low end, also crossing over the mains with the Rythmiks plate XO, and currently with external digital crossovers and each step was an improvement.
The 12" is going to be enough. Yet I suggest going with the 15".
Are JL Fantom better? Most likely, as you would expect given the price difference. But two Rythmiks is better than one JL in my opinion.
I tried them with the full range speakers running full range and the subs supplementing the low end, also crossing over the mains with the Rythmiks plate XO, and currently with external digital crossovers and each step was an improvement.
The 12" is going to be enough. Yet I suggest going with the 15".