A DAC will sure help out the 980. Tube or SS, that's your call.
I'd prefer add a tube preamp at this point were I in your shoes.
Before that though, I'd consider cabling. Power cables, ICs... etc.
That Oppo and the Rotel amp both respond well to power cord upgrades. Also, I'd fiddle with the isolation (footers) and maybe even a damping weight set on top of the Oppo.... I prefer Herbie's iso cups with the Ebony balls for mine.
it will suprise you what just some footers and a pc for that Oppo can do. For the amp too.
A tube preamp however would my my goal ultimately.
I'd prefer add a tube preamp at this point were I in your shoes.
Before that though, I'd consider cabling. Power cables, ICs... etc.
That Oppo and the Rotel amp both respond well to power cord upgrades. Also, I'd fiddle with the isolation (footers) and maybe even a damping weight set on top of the Oppo.... I prefer Herbie's iso cups with the Ebony balls for mine.
it will suprise you what just some footers and a pc for that Oppo can do. For the amp too.
A tube preamp however would my my goal ultimately.