For under 5k used you can get a rogue RP-7 and some nice NOS tubes. I'll agree with bdp24 though when he says a preamp is unlikely to solve your problems. If there's not enough stuff in the room and it sounds too live maybe appeal to your wife by seeing what could be added to soften thr room. Like put a rug down if it's a wood or tile floor. Or get some window treatments if there's a lot of glass. These types of things, while not nearly ad exciting as buying a new piece of gear will make a marked difference in how the room sounds.