I really like Thesis for both mainstream and adult. I think they're also about to release Thesis 2.0, likely with a price increase, so its definitely worth it to buy now. Even if 2.0 doesn't meet expectations, its worth the cost for 1.82, which is what I use.
http://diy.headwayorthesis.com
The new headway looks really good too, but I haven't used it yet.
http://hthemes.headwayorthesis.com/