It seems easier to find Sora than Tiagra. Usually on ebay Tiagra is more readily available. Good luck
Tim
I don't like Sora shifting because of the inability to downshift in the drops... Otherwise, Sora did occur to me.
Even though I will be on the hoods most of the time, I think the inability to downshift in the drops would bug me... even though it wouldn't be a real impact often enough that I should let it be a show stopper.