[QUOTE=dbg]Then you should know I plan to expand the range of that bike for next year's trip
(http://dbg.home.att.net/featurebike1.htm)
by giving it two front rings. This will require a rear derailer to take up the extra chain and a front to switch rings.
QUOTE]

You can do without the front derailleur and manually shift the front rings if you want to save some complexity. you could also use a chain tensioner instead of a rear derailleur if the chain rings aren't too radically different in size.

On my bike friday, I have a sram 3x7 rear hub that I love (21 gears), but I also run two rings up front - a 39 for loaded touring and a 52 when I use the bike as a roadie. to switch the rings, I just do it manually, otherwise, I'd have three shifters, which just seems excessive.