I don't know about the P55A - they could be a 'premium' line of P55 motherboards, instead of a new revision of the current P55 range. (...)
I think the only difference with P55A is it has USB3.0 and SATA 6gb/s. I'm hoping its just a precaution changing socket clips to apease the masses. (ie: sense of security)
Hi
Here is some info about P55A mb's, they also have more power in USB (3 times more):
http://forum.giga-byte.co.uk/index.php/topic,763.0.html