Depending on what you want to spend, I've used a Gammell long-arm and a Tin Lizzie 18 and I'd prefer the Gammell, lots of bucks. The Tin Lizzie 18 can be used on a smaller frame for small quilts around 50" wide. Would be great for baby quilts and they run about $6,000 in our area. You can look at them at www.tinlizzie18.com.
I do think that your dear lucky wife needs to pick out the quilting machine that she wants and you can have the satisfaction of going with her and seeing her make all those important decisions as to accessories that she has to chose from. She is one luck gal. You can always ask dealers for brochures of their wares and put them in a card, that way she knows that you've done research and thought into the gift.