Well, I've experimented again with it...just a little, on low gain, but I really had to crank my amp...which isn't a good sign for the amp.
I'm getting a much better sound out of it.
I demoed Neil Young's "Tonight's the Night" and A/B it against my old rig. Yes, I think the DX90 is an upgrade, so I don't think it's about pairing. I chose that song because of it's funky dynamics, and anytime the tape hiss doesn't sound strident, I think you're on to something as a reference sound.
So, basically I'm thinking I just need a very good amp, one that will stay clean and transparent, while leaving the DX90 on low gain.
Really, I'm thinking the DX90 is pretty good kit for converting a digital signal.
I'll just go ahead and let it burn in for about 10 more days after this without touching it and see how it goes. This is fun!
If you use an external amp the gain setting doesn't matter as it only affects the head out not the line out