Yes... I've thought about upgrading to the SEAS woofers also, but wasn't sure the improvement would be worth the cost, and difficulty. I seem to recall that Don Naples said I had my ASP upgraded to the 3.4 (I sent to him to upgrade - don't recall the details), but I still have the Peerless woofers. He did say I would need to replace a couple of resistors (or something) on the board, if I upgraded the woofers, and there was some minor spacers to add to fit the woofers in the current baffles.
I'm not sure who I could have upgrade the ASP - I'm not sure Don is in business any longer.
I've also considered getting the Madisound kit and cabinets and building the LX521's - but, again wasn't sure the improvement would justify the cost and effort.
Perhaps, it would be best to discuss via messages. Maybe you could send me a message, or how I can contact you.