You already mentioned bearded irises, which was going to be my suggestion. I've had a similar issue with a lag in color in the garden between spring bulb time and when a lot of late spring perennials put on a big show. I have found Intermediate bearded irises (usually just called IB) fill that gap beautifully. They're shorter than tall beardeds, but still tall enough to be seen well in a big garden- 16" to 27.5" in height, and the bloom size is comparable to those of tall bearded varieties. While everything starts earlier in your area, I think the progression of bloom time is similar.
