Hi Padster and welcome. I have to agree with Big Billy about the 4 cylinder 600's being a bit rev happy. I ride a 600 Speed 4, It red lines at 14,000 revs but the power band comes in at 3,000 revs, for the inexperienced this can be a bit daunting as you suddenly whizz down the road while pulling away, they are great fun though. The 675 triple is a more refined and easier sort of ride, that will scare the pants off you if you want. I'm 5ft 7ins and getting on a bit now so my boy racer days are coming to a close. My next bike won't have clip ons it'll probably be a cruiser or an old Bonneville again. Have fun looking, and pick the one that tells you, you're mine. you'll know it when you see it.
I suppose a lot depends on the extent of your back problems, what type of riding you will be doing and the size of your wallet. If you're back is bad you might not want to lean forward. If you are doing a lot of high speed motorway mileage you might not want a naked bike. If you've got lot's of dosh buy a Daytona, a Street Triple and a Bonneville America. Lot's to consider.
Thanks Andypandy, Yes I will be doing some motorway miles, I was thinking about maybe handlebar risers but i'm not sure if it will effect the ergonomics of the bike? Looking at maybe £3500 for the bike and I've seen a couple of Daytona 675's around the 05 plate, do have any rough ideas of service costs? and how many miles between services?
Download a copy of the service manual here: https://www.manualslib.com/manual/801932/Triumph-Daytona-675.html#manual - that will give the servicing intervals etc plus more.
Hi Padster and welcome to the forum looking forward to seeing your ride and wish you well on your search