You can change the BIOS and set the max frequency that u want, independently from the value set by the producer.
However my cards became unstable over 2200 (I am using 1750 timings)
Which particular cards are you speaking of?
Try higgher, just dont save it to BIOS. Worse case you get artifatcs or BSOD and just restart machine.
I appreciate your advice, however I remain reluctant to go any higher than 2300 until a knowledgeable member deems it safe.