FenceFurniture - put me down for about $250 worth of the drills.
In terms of sharpening the Colt forstners, this can be easily done using just a fine diamond hone (like the DMT), plus one small curved diamond needle file. The actual cutting edge is designed so that the bit presents just one large flat surface to be honed, and there is only a tiny portion of curved "nicker" on the outside of the cutter that requires the diamond file. This is in contrast to conventional forstners which present a multitude of curved/serrated surfaces needing to be sharpened.
I've had my Colt forstners for about 12 months, used them in a variety of hardwoods with a drill press (including some quite abrasive timbers like brushbox), and have only needed to resharpen once so far. Haven't used them on a lathe, but I believe some other forumites have tried this (with the extension).