What is the simplest way to lower the gearing on my touring bike? I have a 2004 Jamis Aurora with a 52/42/30 triple and an 11-32 cassette in the back. 30x32 (25.3 gear inches) being the lowest gear is frustrating for the hilly terrain where I live (e.g., 7% grade average over several miles, with higher local steepness), and so I'd like to lower my gearing.

I'd like advice on how to most simply do this. The basic problem is that replacing any given part appears to have cascading compatibility issues which may or may not be solvable, and I'm becoming confused.

I do use the full range up to 52x11 (127.6 gear inches), but only on descents that are fast anyway, so I am happy to lose the higher gears and coast instead. There is essentially no level terrain where I live.

Relevant specs (all parts stock in 2004):


9 speed
Crankset: Truvativ Touro 52/42/30, 130/74mm BCD
Front derailleur: Sora 28.6mm, clamped
Cassette: SRAM 11-32
Rear derailleur: Deore SGS
Shifters: Tiagra
Bottom bracket: TruVativ sealed cartridge, 68 x 113mm


Options that I've found so far:


Add a larger cog in back, such as the new Shimano 12-36 cassette. As far as I can tell, this will require a new rear derailleur and a new chain, but that's it. This makes the lowest gear 30x36 (22.5 gear inches), 12.5% lower, and the highest 52x12 (117 gear inches). A downside is the excessive size of the rear cassette.
Replace the crankset, for example with a 48-36-24. This makes the lowest gear 24x32 (20.3 gear inches), 25% lower, and the highest 48x11 (118 gear inches). At first glance, this one is the most appealing, but it seems to also raise the thorniest compatibility questions; the ones I'm aware of so far are (a) finding a front derailleur which is compatible with both my road shifters and the smaller large chainring (one possibility), and (b) differing chainline offsets of road and MTB cranksets.
Swap in a lower granny chainring, say 24 teeth, resulting in a 52/42/24 crankset. My concerns here are (a) whether my derailleur can handle the 18-tooth jump between low and middle and/or the lowness of the granny gear, (b) the awkwardly wide jump between low and middle (75%, or about 5 sprockets), and (c) retaining very high gears that are feasible only for making a fast descent faster.
Swap in 3 new chainrings. This seems to raise similar concerns to item 2.
I think everyone has provided some pretty sound advice, especially Daniel Hicks and his recommendation to go with the quickest and cost effective option by replacing your chainrings! With a 130/74 BCD, an ideal setup would be to swap in a 24/36/48 which would give you a great range at a cheap price.   

The front derailleur is probably the least necessary component on your bike and, while shifting compatibility is a concern, I would recommend swapping in your new chainrings and setting everything up to test for compatibility before spending more money on a new derailleur. I have used mountain FDs on road triples and road FDs on mountain triples with a variety of indexed and non-indexed shifters and have had very little trouble over the years. Really, the only requirement is ensuring that the front derailleur is a triple and has the correct seat tube diameter/pull direction. (Your cascade of compatibility issues is something I've dealt with, but don't worry! There are lots of manufacturers who design compatibility issues into their gear, but they generally don't cater to the average touring enthusiast.)

Since you have an SGS derailleur (long-cage) you shouldn't have any issue with chain slack. For touring, the Deore SGS set up with an 11-32 is a great choice. At most, you may prefer to remove 1 or 2 links just to clean everything up. (I ride in New England on 24/38/48 x 13-32 and even with a full load I maybe walk it once a year).

When you start changing components such as your crankset you have to deal with special tools, frame clearance issues, bottom bracket fit, and Q-factor (the horizontal distance between your pedals). Mountain cranks have smaller BCDs but have much wider Q-factors which, for some people, can cause knee and hip irritation (which is exacerbated by long rides and clipless pedals). Long story short, if you are comfortable with your bikes ergonomics on long rides, leave it (or give yourself enough time to work out the bugs before attempting a 2k fully loaded). 

Otherwise, take things one step at a time. If smaller chainrings don't give you enough oomph, throw on a new cassette which is quick and has few compatibility issues (12-36 is a common low touring range). More compact road cranks have a 110/74 BCD which won't help you on the low end (though, if your leg length permits a longer crank arm it might provide a very small advantage). Some mountain cranks have BCDs as low as 58mm x 20t, but I suspect that this option may be more trouble than it is worth. Some handy online gear resources include: rivbike.com, velo-orange.com, universalcycles.com, and sheldonbrown.com.

A cheaper way to ease the inherent suffering of long, steep climbs would be to trim some bike fat and touring load (a good technical and philosophical resource might be The Ultralight Backpacker by Ryel Kestenbaum or Just Ride by Grant Petersen). Some people might recommend trimming some actual fat, but we live in a world where everyone gets to ride a bike, not just 130 pound-25-year-olds. (No offense to the 25-year-old cyclists out there!)