Touring - Newbie Crank Question

Just finished my 1st tour (albeit very light) a 4 day trip from Santa Barbara to San Diego and I am hooked. I purchased a Cannondale R400 circa mid 90’s on craigslist that I tuned up and made some minor adjustments (chain, pedals etc). It is equipped with a very solid Shimano 600 6 speed, the front ring is a 52/43 and I put a 14/28 mtn freewheel on the back. The lack of low gears was not a huge issue, but noticeable on some of the climbs. I did not use my large crank once.

My question is this, what is my least expensive option on improving my gear ratio given the components? I have been told that a compact crank might be the simplest, or can I upgrade to a triple without changing too much.

Cheapest thing would be to swap the 43-tooth chainring for a 39-tooth ring, though it doesn't change the gearing all that much.

Compact cranks are a semi-recent invention. Most new ones are designed to work with 9- or 10-speed drivetrains. Dunno what happens if you try to mix a 10-speed compact crank with an older 6-speed drivetrain. Might work, as long as the chain isn't too wide and the chainline is similar.

Switching to a triple would require a new shifter (if your bike has indexed front shifting), new front derailleur, and the new crank. You might also need a new bottom bracket, shift cable, and chain.

I think sstorkel is right about the 39t chainring. You could also check out a 14-32 or 14-34 freewheel. Your rear derailleur might need to be replaced for a 14-34, but might work with a 14-32. I do not know all the 6spd freewheel combinations, but you might find a 14-30 that should work with you present rear der.