I know this community loves the schitt gear, but yeah, seems like I haven't heard many impressions regarding how that line pairs with Grados either. I do know of a guy I correspond with from time to time over at Audio Circle who loves his RS1s with his Schiit amp, but it would definitely be interesting to hear more impressions from other Grado owners who went with Schiit.
I went with Valhalla for the RS1i (even though I think Asgard is way more versatile) just to continue the all tube "rut" I've kept myself in with my speaker amps and preamps for years. It's very revealing and textured, what I love with tubes. No problems at all driving the Grados. The only ss amp in use for me now is the Stax SRM1 Mk2 Pro.
I was tempted when I recently saw a Mapletree for sale on Audiogon, but decided it would be ridiculous to do that while in the middle of Bifrost Dac upgrades. Have heard only good about Mapletree/Grado though.