Best bicycle touring bike components?

I am want to build a touring bicycle to go on long tours. I am getting the Soma Saga frame set. I am having trouble finding which components would work best for my needs. The touring will be done in the USA on paved roads/highways mostly but the ocasional dirt road might come along. I have found the: Campagnolo... show more I am want to build a touring bicycle to go on long tours. I am getting the Soma Saga frame set. I am having trouble finding which components would work best for my needs. The touring will be done in the USA on paved roads/highways mostly but the ocasional dirt road might come along.

I have found the: Campagnolo Veloce series, SRAM Apex series. and Shimano Tiagra series but I dont know if these are right for me. Any and all info able to be given will be welcomed.
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