Buy all of them and get N+1 out of the way.
I would just get test rides on each of them. There will be one screaming "Buy Me".
And already mentioned The Felt has more "Bling" than the others- but only if you can get comfortable on it- And the Sequoia is a known product. I am surprised the the shop did not mention the "Roubaix". The next grade up on bike to the Sequoia and is a favourite here on the forum.
Can't offer any info on the Scott as I do not know the bike.
And lower back pain on a road bike- Just done 40 miles on the TCR with the bars 2" below the saddle. Longest ride so far this year- I think- And the back is fine. Have a bit of neck ache but that will improve with Practice. A longer stretched out position on the bike does suit some back problems.
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How long was I in the army? Five foot seven.
Spike Milligan