With that player, I would agree wholeheartedly - use HDMI and forget about it. Whatever DAC's the Model 978 use, it should be at least as good as the Model 990 sonically (most likely even better - although I prefer to wait to hear it until I say anything definitive). That will be a solid upgrade over whatever analog section Samsung tossed into that player.

Analog performance is a complex puzzle, and predicting it even with specific details on the components used is not practical. Even if two products use the exact same DAC chip, they can sound different. The BDP-93 and BDP-83 are a good example. Both use the same Cirrus DAC, but the BDP-93 sounds a bit better than the BDP-83. Add to that the fact that we don't know what chips the Model 978 is using, and it's far too soon to know how the Model 978's analog performance will compare to other products - especially once you move into the realm of products with above-average analog designs.