I cut my spirea to the ground every fall. They come back lush and bloom well.

Are they pink to rose early summer bloomers, or white spring bloomers?

If it is the former, cutting them back in the fall or early spring is often a good thing. If they are the larger growing white flowered sprireas that bloom in the spring, they I wouldn't cut them all the way back. Perhaps half way. Then when new growth starts in the spring, that should include sprouts from the base too, you could selectively prune more. With this second type, after pruning there will be no flowering the coming year, as they only bloom on wood that has gone through the winter.