I started C. brachytricha this year, but got no blooms (yet?). A. calamagrostis is on my Jellito seed list for next year.

Calamagrostis brachytricha will supply your later season 'fat blooms'. Quite a lovely grass ~ if you do a search you will see a discussion of both these grasses a couple of months ago.
Achnatherum calamagrostis blooms about the same time as your Calamagrostis 'Karl Foerster' so .. not really a solution there. Achnatherum calamagrostis is quite slow to form a patch from seed AND is very whimpy when it comes to other plants seeding into it. STILL ... it is one of my favorite grasses! When it is in bloom nothing can beat it.
A.

Ach, your garden shots are abfab delish.

I definitely lust after the heads of Brachytrichia but am thinking that the Achnatherum has to come play as well.

and then little bluestem has to find a spot and then that Deschampsia goldtau....oy.