I haven't so much upgraded my Triban 3, as made a sideways step to solve a problem.
As you know......the T3 comes with 2300 and a Sora front mech. The 8spd triple takes a bit of fettling to run sweet but can be done with a bit of cursing. I like 8spd - it seems tough and shifts well when adjusted optimally for me. Also...my only experience of Shimano sti has been with those 'mouse-ears' shifters.....and I find them very intuitive and far more convenient than the huge 'grind-and-find' ships levers I had on my old Mercian,....gloriously retro as it was.
I did, however, invest in a new 'Claris' r/d to solve the problem of inadequate clearance between the mech and my new r500 wheels. The claris looks to be EXACTLY a reissue of 'old' 8sd sora and, as such, is rather better designed and altogether slicker and more adapatable than the chunky 2300 d/r it replaced. Also solved a problem.
I think that Claris is probably a slight all round improvement if you want to keep your 8spd set up....and looks on first acquaintance to be a marginal step up from 2300. I would be interested to hear anyones experiences with the the 'proper' dual lever shifters and uprated chainset/bb too? Claris does not yet appear to be mainstream on many new entry-level machines yet, so opinions are hard to come by.
w