Pioneer BDP-09fd if you plan to use the analog audio ouputs. Sound is tonally richer with more body and transient slam than either version of the Oppo 83, though I can't comment on the Nuforce Edition of the Oppo. Visually, Blu-ray video and DVD upscaling are slightly in favor of the BDP-09, but that difference is small and may not be worth the price. It's the audio (and the build quality) that make the Pioneer worth the cash over an Oppo SE. The bonus is that Redbook CD from the Pioneer clearly bests the Oppo, and every other Blu-ray deck with the possible exception of the $6,000 Marantz UD9004 and the $8,000 McIntosh MVP-881 and even that's not certain.
You don't even have to modify the BDP-09 for it to sound steller. I suppose anything can be improved, but the Pioneer is well thought-out and executed from the factory. If you're only passing all signal from the player via HDMI, then the standard Oppo 83 is fine.
Phil