I'd make a list of what features you use with your gecko, and what features you would like, but don't have now. It may end up there really is not a better replacement for your gecko on the market. Or, perhaps, you really want a high sensitivity receiver, want it under $100 and don't mind adding two ounces.. so, the Garmin etrex h might be worth a shot. Or perhaps, you don't care about routing or displaying raw coordinates, simply having high sensitivity and ability to add waypoints, create tracks, trackback... then, the forerunner's might be worth looking into.
I guess my point is there really hasn't been a gecko 201 replacement. As far as I can tell, the foretrex line is probably the closest, but changes the form factor. Getting an idea of what features you enjoy now and what you want to add might help.
If you are considering other brands, my purely personal experience has been good with Garmin and DeLorme, not so much with Magellan. I have not tried any Lowrance or Sunnto units.