That Garmin 7410 is a good starting point. and your existing tm260 could be interfaced into that system. id consider sticking to the current 74xx Series systems, networked.
we started a quickdraw community "a month and a bit before the official garmin quickdraw community made it obsolete" and its been great for us down here in gippsland,Vic etc. its a decent system that will just get better as more people use it.