I've had those heads on my to-buy list for ages and I would have sworn they were suitable for Imperial Assault.
This thread may have saved me from uttering some very rude words had I actually gone ahead and bought them
Mel Miniatures do Clone Troopers, but also Legion sized. I keep on meaning to email him to see if they would put up IA compatible figures but haven't got around to it yet.
He also does a bucket load of x-wing and armada scale miniatures. I've been resisting getting them, but it gets more difficult every time I look through his store