To swap or not to swap...

It's been a few weeks since I picked up my bike and I was eagerly awaiting my SRAM Force cranks. After a few phone calls, the bike shop told me they had it. In the meantime, I had ordered a 11-25 cassette on eBay for pretty cheap. When I get to the shop, the kid tells me they could only get a SRAM Rival crankset so I at first say okay and then hop in my car. I drove about 5 miles and then decided to turn around. First, I didn't want to downgrade. Rival is not the same as Force; I was already kinda sweating the fact that my all-Ultegra bike would be running different cranks. Second, I figure I can just get an even wussier cassette, like a 12-28, if I really need some lower gears (I'm going to Google a ratio calculator right after I'm done here). So I turned around, went back to the shop, and got my bike. I still have a complete groupo and I feel better about it...