When I had the drivers in the mMar-Kel70s I needed the subwoofer to complete the sound. These microtowers are just so well balanced period; the sub is now optional. When I walk around the room the sound is evenly dispersed. Note that I have not stuffed the cabinets, They are just lined with felt. As mentioned above, the image is beautifully centered at the top edge of the desk when I am sitting here. Raising Sand by Robert Plant and Allison Krauss is just stunning.
It has been a couple of years and the microtowers have been great. However I now have 4 Alpair 7ms drivers. What do I need to modify with the port to make them work? Current ports are 3" dia by 4" long for the EL70s.
I transitioned from EL70 to Pluvia 7.2HD in my Castle microTowers and no port mods were required at all. The only challenge was the difference in driver dimensions, which may be an issue for you too. Certainly best to wait for Scott's response on the port, but I recommend comparing the dimensions of EL70 and A7MS to see if you are going to need to modify the boxes to accept the new drivers.
By the way, you are in for a real treat. The EL70s are nice drivers, but Alpairs/Pluvias really cover the treble end so much better.