I don't believe we're supposed to do anything but share our own medication experiences here, but I'm thinking that maybe waiting to see how 300 mg Seroquel XR works might be worth a try, if that is what your doc wants. Seroquel XR can be a monotherapy, and I've read that 300 mg is the recommended dose for bipolar depression maintenance. Look at almost any major site regarding dosing. I have bipolar type 1, but I know that many with other bipolar types benefit a lot from Seroquel. I'm, personally, much fonder of the XR over the regular instant release. For me, Seroquel XR is quite helpful for pretty much every aspect of my bipolar disorder.

I do not have PTSD, though I have had mild traumas in my life. I know many people's bipolar is triggered by stress/trauma.

I'm only sharing my opinion/experience on this, not any expertise, but I hated Depakote. It was very good at controlling my mania, but useless at preventing or easing my depression. In fact, I credit it for even causing the worst depression I ever had in my life (I'm over 40 years old). Almost ditto for my nephew. Of course others may have better experiences. I despised its side effects. I think more than any other medication I ever took, though a couple were almost as rough, but in different ways. Yes, blood tests are involved, though in my case, fewer than when I was on Lithium. Of course if a doctor recommends it, one could be really helped by it. If they don't recommend it, I, personally, wouldn't fight for it.