the PA1 Biamp modules are a nice addition. They come up from time to time on Ebay or here on Agon... I think they fit L1290s and L1590s, but not sure. In some ways the L1290 and L1590 are basically poor-man's-Aerials. The philosophy is similar (no surprise there). By the time they got to the M-series stuff, Mike was out of the picture I think. (had left to start Aerial)
-Ed
-Ed