If you want an improved 2x3 Crown Graphic (Speed Graphic with no focal plane shutter, possibly some rangefinder coupled lenses), look into 6x9 Horseman cameras. Here's a link to get you started:
http://www.cameraeccentric.com/html/info/horseman_2.html Google around, look at selling prices on eBay, ... You should be able to get the little Linhof's functionality and performance for much less money. Horseman VH and derivatives are pretty common on eBay. Accessories too.
If you want a 2x3 monorail, look into Arca-Swiss and Cambo. Both are uncommon. If you go Arca-Swiss, try to get the binocular reflex finder. I had a chance to play with one last June, its great. That the lens mounted was a 100/2.8 Planar helped. Also look into 2x3 Galvins, there are a few on eBay now. I was never fascinated by them but they have their partisans.
Me, I use 2x3 Graphics and 2x3 Cambos, have several of each. Before you give up on y'r Graphic, think hard about what you want to accomplish. If you want movements, go Horseman or Linhof. If you just want interchangeable lenses, stick with Graphics. To get an idea of what can be done, read my lens diary:
http://www.galerie-photo.com/telechargement/dan-fromm-6x9-lenses-v2-2011-03-29.pdf