Having heard the La Scala's on many different occasions, I can also attest to them lack somewhat in the low end. There are several upgrades you could consider, I would recommed building some CornScala's which is a combination of the La Scala's mids and tweets, with the Cornwalls woofers. This would probably go down to 30hz or so. I would sell the La Scala's and purchase a CT-125 tweeter with it's stock horn and a Selenium D405 mid-range driver with a JBL clone M2380 horn for the mid, then go with a CW1526 all from Bob Crites.
This would be a very very nice setup! The Seos speaker kits are also really awesome, but I am not so sure that it would be that much of an upgrade. You could do a Seos-12 + DNA-360 + AE-TD15x, which would be nice and likely have some good mid-bass, but I would bet the CornScala would best it.