I actually haven't heard anything the Modi doesn't pair well with. It's really that good and I do believe it's very neutral with no emphasis anywhere.
I compared it for hours with the ODAC and found them so close in sound that I ended up selling my ODAC. Both are good.
Neither are super revealing detail monsters and almost a little forgiving. I actually did not hear this until I tried the T90 and got a new (slightly more expensive) DAC.
I think the Modi is one of Schiit's best products and i'm kind of a fanboy of it. I probably sound like I hate Schiit products but I've been through so many of their amps and disliked most of them. Magni was pretty OK. I should probably stop buying their stuff already. The Vali just left me frustrated and annoyed.
BTW IMO the Modi is easily one of the best budget DACs (under $200) there is for the HD-650. Can't go wrong with the ODAC as well. Some say the ODAC is better but I couldn't hear it. I actually had the HRT MSII before buying the ODAC.