Biller is a furniture shop near Moosburg, on the outskirts Munich. They're good for sofas.
Its a long way out from Munich center but they had just as good a selection as Segmüller but at better prices. Better and friendlier service too.
Biller service is great. I bought my kitchen off them when I moved over here, and despite numerous problems to do with the language, they sorted everything out perfectly.
I bought a Sofa in Segmüller recently and the service was fine - probably at the same level you'd expect in the UK or US. Much better than at Karstadt where the salesman was like "Take it or leave it, I don't care".