Just hooked up the LSI15 to my Yamaha RX-V1800 for the first time. I dont have my amp yet (the Adcom amp is arriving this week). While playing Mp3s weren't that impressive (probably because of the quality of my mp3s). Playing BluRay (ratatouille) was amazing. I've always had crappy speakers so this was a big upgrade. The imaging was amazing.
The FXI3/FXIA4 (yes I know they dont timber match :)) also sourrounded me with amazing ambiance sounds (ie: when the rats were making an escape in the water, it felt very realistic as the sounds of water was everywhere around me)
I can't wait till I hook up my 3 channel amp!