The issue is, that you probably want an amp with line-in sense/autosense (means that it turns on/off by the source).
Otherweise you would need a remote control for the amp.
Since you speak of 3 rooms, you would need 3 amp....with the opportunity of looping through the signal of the BS Core from one to another.
Unfortunately I don’t know of any ‘cheaper’ solution for that than the BeoAmp 2’s.
Depending on the placement in the house, this also involves a great deal of cabling from a central point.
Another option (with less cabling) would be to install a set of BS Core and BeoAmp2 for each room.
Maybe you could convince your wife to get one or two pairs of the BL4000’s, which can be installed rather discrete.
This would lower the costs, since a pair of preloved BL4000’s come cheaper than a BeoVox2-2/BeoAmp 2 combo.
P.S. If anyone knows of a non-B&O amp with the needed options, I’d like to know it, too!
MM