I have the Brother CS6000i and it is a great little machine and very light. It does come with a walking foot and the only accessory I had to add was a 1/4" foot. And I love mcwillia's idea of an extra set of "traveling tools" - your wife would appreciate that, too, I'm sure. If you get the Janome gem, then your wife will have two gems - the Janome and YOU!
Just saw amythyst02 post when mine came up -- and she's right -- a surprise shopping trip rather than making the machine choice for her. Or you might consider purchasing the travel case for a machine (which can be returned without much hassle if it isn't the right size) and give her that with a note inside that lets her choose what to put into it.