Less is more?

[etherealbike]

So, I have a daily commuter/light touring bike (Schwinn World DBX 2007) which has a triple crank-set. My question is, can I come up with roughly the same gearing (on the low end) by switching to a dual compact crank-set and changing out my rear gears to a lower set? I would have to change out derailers and shifters, no?