I've never had anything Ultegra level, I can't spin fast enough to justify it. In all honesty, I can't feel any difference in my full 105 Felt 70 and my mixed bag home build with Sugino cranks. I would spend on the BB, but the cranks (unless very heavy) aren't going to make that much difference. On a touring bike where you set your own pace I would think 105 would be fine, I've done several centuries (solo as well as group) on mine.