Based on a brief bit of googling, I would expect the 990 to be an improvement over the VR8070. The move to separate amplification was a good first step and has already served you well, but there would likely be additional benefits in the 990 upgrade.

Yes, you can connect both the DVD player and DirecTV HD receiver to the 990's DVI inputs and run from the 990 to your Sony (along with coaxial or optical cables for each).