> need more oomph in my bass and that seems like the best way to get it without losing the qualities I like in the Sundaras.

You can also try the Edition XS. Recently got these and to me they fill in the exact holes that the Sundara is missing. The bass sounds like a flat line pretty much all the way down to 20hz, and it has noticeably wider soundstage and even better instrument separation. It's definitely not as intense in the mid-mids as the HD650, so it might be up your alley.

Of course if you're set on the Arya that should be flat out better in terms of technical ability, but they ARE supposed to be brighter...