I just found a used SLR saddle for $30 that's going on my IRO. I just love the SLR XP on my road bike. I just did 20 miles in boxers and Old Navy chinos (no padded shorts) and my butt doesn't hurt one bit. I'm 5'5" so my sit bones probably are a perfect fit for the narrow minimal SLR.

That said, the key to not having a sore butt is to find a saddle that supports your sit bones, not too narrow and not too wide, and IMO the less padding the better. The saddle should be level so as to support your sit bones and the fore/aft position and stem reach should be adjusted so that your weight is balanced between your sit bones and arms. If the saddle is too far forward, you're resting too much weight on your sit bones.