Because of the way I currently have the shaders set up, I tend to have an extra copy of them for the express use of the non-displacement mapped pieces (those without bumps on top). Apparently, for every piece, you need a seperate displacement node.... even if their components start out in the same location.... ah well.
And I've tried bump maps - they didn't look 'real'. Might have been the lighting angle, but other than that they looked too flat. And for how close - well, I might get closer than this; although the cylinders are fairly low poly (32 axis divisions) , they're effectively normal-mapped (from the program defaults). So I actually can get quite a bit closer before they break down. I think.
Might try getting more resolution on the top - but it's just the standard axis division up top. Thanks for the idea, though.