[GSsixgunner' post on the BRM formula]
Fine basic white & the dutch oven approach works well. If you branch out into the whole grains, you'll get a new avenue of flavors (said the spider to the fly :) ). Keep the whole grain content to 15% or less & you'll still have a good rise. More, and you'll have issues. The wheat/rye blends can be nasty good. 1:2 Rye:Wheat works well.
Another flavor trick is to substitute coffee for water.
Another is to thin-slice some older slices ('bout 3oz), toast, break into tiny chunks & pour 16oz water over & let soak overnight (Old Bread Soaker). Reduce the water in the final mix by the 16oz used in the soaker - keep the hydration in the ballpark.
Another way to crank flavor is to extend the time the dough spends fermenting - usually by refridgeration. I've not done w/ commercial yeast, but the bio cycle is similar. Colder temp slows the yeast & lets the flavor bacteria propagate.
If you have a good hit on a rich sourdough - we'll stick a fork in ya - you'll be done. :)