I know exactly how you feel; Seroquel is effective for so many things but SO oh SO sedating, including the day after. You're taking a pretty high dose, are you sure you can't sleep with a lower dose or with a different medication (are you only taking it for sleep?)

I also need at least 9 hours of sleep on Seroquel. It doesn't put me to sleep, I quite literally eventually pass out if I attempt to stay awake once it's really kicked in. I've actually been falling asleep at the wheel on the way to work lately and am planning on slowly lowering the dose I take.

Anyway, so I get it. The only suggestion I have is to try something else for sleep if that's all you're taking it for. Seroquel is a really tough one, I wish I had better answers for you... Good luck.