And 53cm?? I'm jealous! that's my exact size too, my custom frame will have a 57cm ST and 53cm TT, exactly your size.
Spotter's bad is the cheapest compact for 26mm clamp, but I find the curve a bit awkward to hold, you might want to upgrade to the Soma HY1 that come in silver too and have a nicer drop shape than the Spotter's.
don't forget about the reach on the handlebar, your old handlebar is likely to have at least 90-100mm reach from clamp to front, whether compact drop are between 75-90mm, the Soma bar actually allowed you to run an 100-110mm stem if necessary with the extremely long hood of the 105 levers.
I would not invested in 105 cassette, just the 10spd Tiagra as it's cheaper and work just as well, no reason to spend more for an audax bike that likely to wear out.
And 53cm?? I'm jealous! that's my exact size too, my custom frame will have a 57cm ST and 53cm TT, exactly your size.
Spotter's bad is the cheapest compact for 26mm clamp, but I find the curve a bit awkward to hold, you might want to upgrade to the Soma HY1 that come in silver too and have a nicer drop shape than the Spotter's.
http://www.sjscycles.co.uk/soma-highway-1-drop-bars-260-mm-clamp-prod28240/
don't forget about the reach on the handlebar, your old handlebar is likely to have at least 90-100mm reach from clamp to front, whether compact drop are between 75-90mm, the Soma bar actually allowed you to run an 100-110mm stem if necessary with the extremely long hood of the 105 levers.
I would not invested in 105 cassette, just the 10spd Tiagra as it's cheaper and work just as well, no reason to spend more for an audax bike that likely to wear out.