@brian_holmes,
You ask a good question, and I asked myself the same question before responding above. I don't have intimate knowledge of either speaker, so I can't answer definitively. I'm going to assume that both speakers are well designed and capable of producing tight bass. I'm also going to assume that by boomy bass you are talking about inarticulate one note bass, ala cheap bass reflex designs from back in the day.
One possibility could be some sort of Speaker Boundary Interference Response difference between the two speakers. Do the two speakers crossover at the same point, and are the woofers mounted at the same height? Is their -3dB response at a similar frequency? Are the CMs in exactly the same position the 602's were? Inches can matter. Has your main listening position changed at all? Have you changed the position of any other furnishings in the room?
This tool could provide you with some insight. Compare the two speakers using the calculator and see if anything stands out.
http://tripp.com.au/sbir.htmBut, without a way to measure what your room and speaker are actually doing, it is tough to mitigate the problem. It is pretty much always true that a change in position of either speaker or listening position will make some aspects of speaker room interaction better and others worse. Moving stuff around is therefore a tradeoff. What you need to do is measure the system as it currently stands, and look carefully at REW waterfall plots. You need to understand the correlation between what you are hearing with your ears and what you are seeing with your eyes when looking at the plots. What I am guessing you will see is a nice smooth decay of frequencies above 200-300 Hz, so that those higher frequencies do not persist at a significant dB level longer than 300-400 milliseconds. But below 200-300 Hz, my guess is that you will see some frequencies persist much longer than 300 ms. This is ringing. I've seen frequencies that will not decay for even 1 second or more. This sort of behavior is not going to allow satisfying bass response. Once you take enough measurements with speakers and listening position moved back and forth, you will have an understanding of which peaks and nulls are due to speaker and listening position, and which ones are due to room dimensions. You can't change your room dimensions, but you can change the position of speakers and listening position. Sometimes you can move a speaker boundary null into a room dimension induced peak, thereby causing them to offset one another.
It is just a pure guess on my part, but I see no reason to think that the CM's are not well designed speakers that are not inherently unsuited for use in your room. So it comes down to determining optimal positions first and adding supplemental treatment second. But don't discount the Swarm system. It's just physics. A DBA is "the right way" to address the problem, if at all possible.
