Firmware can only fix an issue that occurs on the printer, not anything that happens client side before the printer is even made aware the job is coming.
As for drivers, you already have a PS,PCL5,PCL6,XPS as well as Global PS and Global PCL driver to choose from, and since they are independently developed by different people and share no files between them, they can't all behave the same, unless acrobat is the issue, or the file is (hint, save as PDF/x, never PDF if you are the content creator of anything meant for print.)
At work we have got a Workcentre 6605. Printing pdfs take seemingly forever, looks like it's because of spooling. I remember reading somewhere that there might be a driver/firmware that could increase the speed but I can't find it anywhere.
Any advice or pointers would be gratefully appreciated.