Most of the popular large-flowered hybrids bloom summmer to fall. This early-blooming "they" you speak of must be some other kind.

Today I saw a couple 5 gallon pots of a striking new velvet purple one blooming at Wells-Medina nursery in Bellevue. Would look good with your colors.

The "they" were the clematis at Molbaks. I thought since they only had only had spent blooms that they were done for the year. I am glad to hear that I am in error. I haven't been to Wells-Medina yet this year, but I am eager to make the trip.

I have several obelisks of various sizes, and love them. Use several kinds of vines on them - annuals and otherwise: akebia, scarlet runner bean, purple hyacinth bean, cardinal flower, sweet pea (in spring and overplant with runner bean later). Hummingbirds everywhere! I like annual vines because they grow fast and don't have to worry about "taking over" since they die off in winter anyway. Akebia is supposed to be rampant but mine aren't.

Many of the Type II Clematis bloom twice, once in spring and once again in fall.

Piilu is one that is compact and a long bloomer. I've got it on one of my obelisks and it is doing great.