I'm perfectly ok with low-powered campaigns, really. I think focusing too heavily on the stats might miss the bigger issue with characters gaining power rapidly. Stats mean relatively little compared to class levels...

So, I suggest you use some fraction of book standard exp for encounters. This has a lot of nice side effects, and keeps progression to a lower rate, while not really messing with much else in terms of balance. If you're feeling generous, reduce exp costs for spells/etc by an equivalent rate.