When I was involved with developing the Creo/Kodak Spotless printing system, we experimented with hex colors and found that they had little value for most images and generated unnatural candy-floss looking pictures. Most printers that I know create bump plates manually in PhotoShop to add vibrancy to images.
The easiest way to test it is to use a hexachrome profile and take an image and compare that image to your current print profile against the hex profile. You can use an application like ColorThink to do that. You'll see whether any image colors are out of gamut for your current print profile but in gamut for the hex profile.
Something like this:
The original image (a snapshot I took in San Francisco):
Its pixels plotted in ColorThink:
Its pixels compared with a standard sheetfed profile - note the out of gamut reds, oranges and blues.
Its pixels compared with a Hex profile. Note that some reds are still out of gamut. The blues are still out of gamut.
Now, are those few bits of color worth achieving on press relative to the cost and hassles of a six color process which uses non-standard CMY inks in addition to the extra Orange and Green?
For most people the answer is no.
I have a hex profile for you to play with. PM me if you want it.
best, gordo