[bob]

My first suggestion would be to try nudging the treble control on your
amp down a bit. Does it sound better? If so, consider investing in a
decent equalizer that will let you adjust things more precisely to
your liking.

Also, what's the room look like? I realize that formal room treatment
is not going to sit well with the SO. But a plush rug on the floor,
some heavy drapes, maybe a little more upholstery (or more
strategically placed upholstery) might help.

The one thing that won't help you is a new solid-state amp. A tube amp
might help, if you can afford one powerful enough for your speakers,
but it's only going to help because it's doing what an equalizer can
do much better--roll off the highs.

bob