Although others may disagree, I'd say that 17 inches is a very low gear, probably lower than you need unless you do loaded touring in big hills. With short cranks, I'd recommend not going all the way to Rocket gearing, either. It wouldn't hurt anything to start out by replacing your 52T ring with a 54T or a 56T. The 56T might be stretching the capacity of your front derailleur, so if you go that route you might end up replacing the inner ring to a 32, which would only lose you about two inches from your current low gear. You could replace all three chainrings for under $100, so it's the least expensive option.

Another option would be the SRAM 3x9 rear hub. Like the Capreo, you'd need a rear wheel built up for it, but the advantage would be 81 speeds and a huge range -- the equivalent of 9 chainrings from 21T to 57T. And relatively inexpensive compared to the Rohloff.