[PJ352]

If you ride on the hoods the majority of the time Shimano's 2300 series shifters will work fine. Both Sora (now 9 spd) and 2300's (8 spd) employ a thumb shifter to shift to the smaller ring/ smaller cogs, but that's only a disadvantage when riding in the drops.

http://www.amazon.com/Shimano-ST-2300-2x8sp-front-rear/dp/B0038EI5K2

FWIW, if you did decide to go 9 spd, as long as you stayed with similar gearing, your RD would work fine.