A sub output could be handy in some installations, however it would not be all that useful in a high end system. It is very unlikely that such a system would make use of the front/rear fade as the rear drivers are strictly for rear fill and once set would not need to be adjusted independently of the front. Most installations I've seen take the sub signal from the front channels (via a crossover) and I can't say I've ever had a problem with that.

Having said all that, I might have been spoiled by the sub gain remote control that comes with my Kicker 405 - not that I've ever turned it down I guess having a sub gain control in the empeg could be useful if we also got individual settings per track or genre.

As for GPS, if someone releases some software, you will be able to plug your GPS receiver into the docked serial port.

Rob