I use a Sailrite LS-1 - it's reasonably priced, and has handled everything so far. Getting a proper table to mount it in is well worth it, and their support is excellent. The "Base" model (better than the cheaper classic) plus the table will run around $1K.

I've posted this link before - I keep a list of resources online:
http://bike.zugster.net/compendium/bag-making-resources
One thing that you really, really, REALLY want for making bags is a sewing machine with a walking foot - it's really necessary for feeding many layers of Cordura and VCP evenly.