Main thing for me is that I don't feel like getting everything recabled. For Sennheisers, it's easy because they have detachable cables. For some other headphones, it won't be nearly as easy.
I think the Balancing Act has both the balanced and single ended options. What made you go for the WA5 LE over something like the Zana Deux? I know Woo Audio has excellent service. What audio qualities that you read about drew you to the WA5?