Yes, I was thinking weigela, before I scrolled down enough to see applestar's response. Very pretty!
And yes you basically have to decide between the oak and the weigela. I have a weigela wine and roses variety with the dark foliage. But it is in a location where it doesn't get enough sun (which is most of my yard!). It hangs in there, but has never really thrived and is sparser than yours. If the oak tree gets bigger, it will shade out the weigela.