Hello bamboo,
I believe you've reached a crossroads on your audio journey. I suggest you need to decide whether you want to retain the convenience of a receiver, along with its inherent limits and compromises on sound quality performance, or you want to upgrade to higher potential sound quality performance through the utilization of separate preamp and amp components in your system. Contemplating using your receiver as a preamp seems to indicate uncertainty and avoidance of making this basic but important decision.
I recommend and encourage you to take the adventurous road on your audio journey. For example, you could sell your receiver, use the funds to buy a high quality and well matched new or used preamp to mate with your 275 amp and begin exploring and enjoying the wonderful new world of increased higher audio system performance that well researched and carefully chosen separate components are very likely to provide.
Best wishes,
Tim