Go back to the LBS. Have them put a different seat on the 7.3 and test ride again. If the seat is comfy, but the 7.3 + the seat. Most LBS offer 10% off on accessories when you purchase a bike. *SOME* LBS will offer "deals" on seats, but probably not on the low end seats on hybrids. But it will be worth asking.

I don't believe you are overthinking this. You are being a conscientious shopper who doesn't want to make a bad decision on a large purchase. All of the bikes you've tried are good bikes. Fit is the most important criteria for finding the right bike.