You may also want to consider upgrading from the Oppo to a good DAC like a PS Audio DSD or an Exogal Comet, both of which have great transparency, detail, clarity and very wide sound stages.
Without knowing your budget I would consider a used ARC LS27 or a BAT VK-51se. I own the BAT. There is one on Audiogon for $3300. It sold for about $9500 new.
Others to consider are the BAT VK-32se, the Pass XP-10 and XP-20