Scott,
What a nice hubby to want to surprise your little woman with something so nice! What a Guy! I say if you do a little research you can find just the right one at the price you can afford. Just make sure it is compatable with her machine. Six hundred dollars is a good price for a little gracie II and if it is the place I am thinking (sew and Vac), they throw in a quilt cad software which is a great deal. I would say one thing though, get the fourth rail when you buy the table, it is less money if you do. Oh and don't forget the cloth leaders! Just ask they will explain it to you when you call.
Check on (watch) the classifieds here on the board too. Sometimes there are some great deals just waiting for you to pick up.