option a) or b) - don't give up the Torii III.... if you don't have the Jupiter caps in yourTorii III - get them installed...!!!!

The Torii and the ERR's will have better overall synergy than ERR's and the SE84UFO IMO. Also.... Zenmaster Steve told me that UFO transformers will likely be an upgrade option to us Torii owners in the future. The Torii is simply an amazing amp sonically(especially for full-range, single driver, crossoverless speakers) and is so flexible.
Have you ever heard the Grado GS1000 cans? These are my favorite cans(overall -
all things considered, impedance, comfort, cost, value, etc.) over everything I've ever heard - and that's a lot, as RMAF has an entire ballroom dedicated to headphone listening and you can audition just about every headphone in existence there, one right after the other.
But headphones tend be even more of a "personal taste" component than just about anything else... so do strive to listen to as many as you can, before shelling out a lot of coin.
There are some very, very good headphones available these days - surprisingly good to me, for not a lot of jack.
I would encourage you to audition as many as you can to see what you like. For a long time, before I bought any serious cans, I researched headphones to death. When I went to RMAF a few years ago and had a chance to audition just a whole pile of cans, I really wasn't that impressed with the more infamous and popular cans, like the Sennheiserv 650's for example.