I don't think that a new sacd player is going to get you much better, if any, perceptible sound quality than your Oppo, but I could be wrong, and plus your Oppo doubles as a good bluray player. I reported above my positive experiences with "lesser" players than the Oppo, so you're probably already sitting pretty good.
Might as well keep it, since you have 400 cds... cds are cheap in thrift stores these days like $1 - 3... I have found many awesome classical selections, top notch, so yeah keep your physical spinner.
Just add a decent streamer. Bluesound Node 130 is a decent easy-to-use streamer for starters, $600 done.
Later you can add an outboard DAC that'll take both your Oppo AND your streamer, IF you even decide that you need it...