That’s a great price for the 770's! I couldn’t blame you for grabbing some. Their overall tone is accurate enough that I don’t think their bass will annoy your personal tastes.
The 990 and the COP are bassier headphones, particularly in the midbass region that’s easiest for our ears to notice. And more-so when you open the sliders on the COP.
If you’re looking for something cheaper that does a reasonable job of mimicking the 770’s sound, you might try to find a Takstar Pro 80/ HyperX Cloud Core/ Cloud II lying around. They can all often be had at a discount, and their audio driver system is a pretty good clone of the Beyer’s, though without their fun enclosure design and large velour pads.