Monitors for rear wall placement and low volume

I was just about to pull the trigger on some Spendor S3/5 for a friend. I felt these, used, would be the best bang for the buck, and would be OK if placed near a rear wall.

Then, I read that they weren't very good at low volumes, and his listening will mostly be done at low to medium volumes.

Should I forget the Spendors? try something else? or do you think the S3/5 would be OK?