Dreaming of large flowered clematis

I came back from a long weekend out of the country to find a single flower on my clematis 'Isago'.  (It has several other buds.)  This poor plant had a really hard time getting established.  I suspect its because it's in a slightly shadier location than my other clematis.  For a couple of months it looked like it was dying.  Then it put out some new leaves, and now this:

I am so happy it made it!  I also think its flower is gorgeous. 

'Isago' and 'Huldine' are my only large flowered clematis.  (Of the small flowered types I have 'Paul Farges', Sweet Autumn, clematis viticella luxurians 'alba' and even the tiny non-climbing clematis integrifolia alba. 

I've been thinking about what I'd like to change in the roof garden next year and one of my tasks is to replace the huge and ungainly stand of sweet peas that has thrived in front of the patio area with some more considered perennials.  The garden needs more plants with either large leaves or large flowers to balance out all the dainty delicacies so I think I'm going to put in one or two large flowered clematis where the sweet peas are now. 

Brushwood Nursery has a huge selection but I'm looking especially at 'Henryi':

'Starfish':

'Candida':

and 'Madame Le Coultre':

Do you have a favorite?