All modern AVRs work fine in stereo mode. At worst, you have to manually configure the AVR to tell it which speakers you don't have. Most modern AVRs include some form of room equalization. When you run the EQ's auto-configuration, it'll detect which speakers you have and configure the receiver appropriately.
You'll have to tell us your budget if you want more detailed help. HK still makes decent AVRs, though, if you want to stick with that brand.