Off the top of my head, Marantz PM700x/800x/KI Pearl Lite all have av bypass, Marantz calls it Power Amp Direct.
There are more options out there but I'll let other c-hings chime in. It would also help if you could provide a budget.
To answer the second part of your question, yes, you'd only be using the pre-amp of your AV receiver connected this way with your L/R speakers, the C/SL/SR would still be pushed by your AV amp.