I'd agree that multi's generally aren't as good quality as dedicated - but that would depend on how choosey your wife is with quality. For myself, I'd never buy a home photo printer, as they are satanically expensive to run. If you want a great quality pic, even up to A4, it would be cheaper to email the file to a print bureau & get them to whack it out as a photo.
But if you must waste money at home

definitely get a 5-cart printer of any brand - preferably 6-cart. The light cyan and light yellow (or light cyan - depends on the system) is the real key to awesome colour reproduction.
Don't give in to the temptation to use 3rd-party inks: all the manufacturers spend massive amounts of money refining their inks for their printers - the "cheaters" don't. Also, if you use non-branded ink, you immediately invalidate your warranty.
Be prepared to spend serious amounts of cash if you print full-page colour on a regular basis...
EDIT: I also strongly recommend straight-paper feeds where possible / practical: means less jams and heavier paper can be used (as in, card-weight - some will do 300gsm!)