Boxwoods don't have extensive roots. In fact they are quite shallow. I think if you just cut down on the roots with a shovel as far around the shrub as you can get then pulled them out with the truck you would be fine.
That's funny that you guys say boxwoods stink. I wonder if it's a variety thing? I take care of a lot of them, real up close and personal, and never noticed a wet dog or pee oder. Maybe my nose is dysfunctional...
On the second part of your question Nacho, I was wondering which direction the flowerbed faces that you were thinking of planting with azaleas or hydrangeas? Why don't you do both if the location is right?
I just ordered a complete shade garden from www.farmerseed.com it is supposed to grow "where nothing will grow" ........ so we will see. I have an oak tree on the end of the house that is desolate underneath.
@baymule , be careful of planting under established old oak trees. The extra water that a flower bed uses can cause them to develop oak root fungus and they eventually die. Not overnight, but after several years. I had a friend that lost several old Engelman oaks after irrigating beds beneath them.
Some oak trees may possibly be more sensitive to this than others.
Don't want to be a downer, just thought I'd give you a heads up so you could look into it.
In Cal. , in a new subdivision where there were quite a few old, older to fairly young oak trees in what was once a arid cow pasture , the builder built homes there. New buyers liked the shade and installed sprinkler systems, planted all manner of flowers, ground covers and lawns. Then 3-5 years later, guess who had no more shade and some fine firewood right in their yards along a nice bill from the tree removal company.