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Ah yes - Royal Blood aren't bad. Buffalode were a stoner/doom duo who were pretty good, but they split up this year.
I like the power trio format, but I've never liked Muse - they just don't do it for me, which is surprising. I think it's the keyboards, but then I like Nice/ELP.
Top trios would be Rush (not seen them live), Manics (although they tour as a 5-piece), Cream (but didn't enjoy them live) and of course Motorhead!