I've got a Janome and had it for 17yrs, is a basic machine so not too much to go wrong. I'd advise going to a sewing machine shop, usually independently owned so good service and they show you how to use. Service and problem solving is always a good thing to have. Ask your wife what she wants it for, ok, sewing I know, but would an overlocker be better for her use. They cost only slightly more but if she's decorating cushions, for eg., or making clothes then the edge is neatened instantly. I'm looking into one now as machines that applique cost loads more and are technically too advanced for me. I do quite a lot of sewing but don't do the craft embroidery stuff, I make panto costumes, clothes, curtains etc.
John Lewis have a good dept. for machines and
http://www.thesewingstudio.co.uk is an excellent (imho) place.