Join Date: Jan 2008
Location: Raleigh, NC
Bikes: Surly World Troller, Dahon Boardwalk, Raleigh 20, and the frame of a Surly Longhaul Trucker
I don't have experience with those specific components, but from what I know of IGH's you will not be able to use a bar-end shifter for the hub part of your 3X7 unless it is indexed specifically for a Sachs 3-speed hub, and I don't know if there is such a thing. The 7 cogs will not be a problem, I expect, as long as your shifters are friction or are indexed to the gear cluster. But you cannot friction shift a 3-speed hub. Or, rather, you can, but it's better not to: better for your hub and better for ease of use.
Also, I beleive Sram hubs maintain the same shifting as they did when they were Sachs, so you may get away with a Sram shifter. I would assume, but could easily be wrong, that the indexing for the hub portion of a 3X7 is exactly the same the indexing for a standard 3-speed hub.