I'm wrestling with this issue myself just now as I want to do light touring in N. Hampshires mountains. For 3 to 4 days, with camping gear, I'll need to load the bike with 20 lbs. of gear, including rear rack and panniers but not including food and water. My bike is an 8 spd triple and my best estimate at the moment is I'll need 25 gear inches. The 30T chainring would be replaced with a 28T and the cogset would be replaced with a Harris Cyclery custom 13-30. If needbe, It is still possible to replace the 30T chainring with a 26. A triple provides quite a bit of choice it seems to me with relatively close gearing.