Definately negotiate this time of year--if you aren't opposed to used machines, many stores offer great deals on machines people "thought" they wanted but never used or learned how to use. A quilt store that also deals in machines can really be helpful and guide you to the right machine for the RIGHT price. Some now cost more than my first car!!! and I'm only 40. :shock:
For quilting, I agree w/ the 1/4 foot, walking foot, open toe foot--all necessary.
How serious is your wife? If she's not really sure, I would not invest a great deal in a new machine until she has a few "under her belt" and makes sure it's something she really wants to do. Then, the sky's the limit with what you want.