Except for the spices, what you have sounds like Westvleteren 12.
Munich, Special B and CaraMunich are all dubbel-like flavors. If you want to make a bigger dubbel, try that. Try dark Munich.
If you want to keep it more Barleywine-like (Scaldis/Bush), use more sugar and some CaraVienne perhaps. See what I wrote on that for the Barleywine article in Zymurgy.
Can you describe the target profile you're seeking? You have a good base, but it depends on what direction you want to go. Color, flavors, attenuation, etc. are what will differentiate it based on what you add next.
Gordon, I appreciate the advice and guidance. Part of the problem is that I haven't settled on what my "taste imagination" is telling me this beer wants to be. I guess the key component is drinkability, with maybe some slight chocolate/rummy/raisiny notes. I think that's why I keep conceptualizing it in terms of Rochefort. I do love the Scaldis/Bush and Westvleteren, so now you've got me thinking more in that direction. Being that this is a "special" beer, I'm shooting for something in the 10-12% ABV area. I figure I've got about a month before I brew it, so it'd be great to continue this dialog with everyone and see what kind of ideas come up.
Narvin, thanks for the link to the St. Bernardus recipe from Kris. Some interesting ideas there, too.