Touring - Need lower gear

I have a '96 Trek 520 purchased used. 46-36-26 triple in front and 12-28 7 speed cassette. Front derailleur is Shimano Sora and rear is Shimano RSX. 25 gear inches is my lowest and I would like to go to 22 gear inches. What's your opinion on the most desireable way to get to 22 inches?

An inexpensive mtb derailleur(Shimano Deore perhaps) and a larger cassette. The RSX der will only go up to 30t in the rear, don't know if that's enough or if you can find cassettes like that.

For me, a 22-inch gear is still way to big for the hills I encounter, my age, and my level of fitness.

I had mountain gears put on my Trek 1000, which necessitated a Shimano Deore derailleur. I changed both the chain rings and the cassette to get the lowest gear possible. I love the result. Good for climbing trees.

We put these Shimano Mega Range (http://www.vwvagabonds.com/Bike/BikeGearing.html) on our old 7-speed Mt. Bikes before touring and they are wonderful. I had to do some fiddling with the derailleur to get it to shift into the largest gear.

http://www.vwvagabonds.com/Bike/images/GearsMegaRange.jpg

trek520 - i am in the process of upgrading the drivetrain on my old trek mountain bike. have you considered switching out the inner chain ring on your bike? If you move from a 26tooth inner to a 22 tooth chain ring, you could achieve a 21 gear inch low gear.

in my case, i have to switch out the entire crankset, because I have welded chain rings, but on a higher end bike like a 520 you probably could just switch out the inner chain ring.