Having done our big furniture shopping, thought I would reply with what worked for us.
We tried to rent a van from Avis etc to drive up to Germany but had a hard timing securing one over a weekend. A local told us about
www.unirent.ch. They have a good selections of vans (for CHF 109 per 24 hours + CHF 26 insurance and 150km free, they also rent cars). I recommend this place as it is easy to get to on the tram from the main station (less than 10 minutes, then a 5 minute walk) and good service.
We did not buy all of our furniture in Germany, but the pieces we did buy are very good quality and less expensive than in Switzerland. Our favorite stores include:
1. Mobel Market in Dogern - Very good selection for tables and chairs, kitchen supplies, area rugs etc.
2. Kreidler in Tingen - great selection of lighting, furniture (we are buying modern, some of the selectionw as too traditional). We ordered a custom kitchen table (takes 6-8 weeks) and they will arrange VAT (our price was net the difference, they do all paperwork), delivery, and assembly (all included in the price).
3. Mobel Dick in Tingen - huge store, lots of selection in everything.
4. Seipp - Although we were in the market for good quality pieces, we found this store very expensive and really no different than the better stores in Switzerland.
In Switzerland we bought at Pfister and Schubiger (the one in Dubendorf has a sort of outlet section; we found a great couch there for 30% off). We also bought a closet at IKEA (delivery and assembly was an additional CHF 500 and in hindsight we could have bought one at Pfister for the same price, and much better service).
Interested in other expereinces!