Yeah... that bupropion dosage is WAY high. For instant release (IR)and extended release (XL) types, it shouldn't exceed 450mg (the IR being divided into 4 doses). And for the sustained release type (SR), it shouldn't exceed 400mg per day (divided into 2 doses). (You can see even more specifics on drugs.com.)

My experience with bupropion (both SR and XL) has been good. But that is with mood stabilizer onboard.

I've not taken cymbalta.

Edited to add -- I've been on none, 150mg(SR) or (topped out at) 300mg, which is where I am now, on the XL.