Well, if you're not sure, then ask if you could test the PS3 right there in the store and see if it has the FW you want.
I would suggest going as to early FW update as possible, because it is possible to update to newer ones, but impossible to revert. 3.41 is the limit, so don't accept anything after that.
Sorry i couldn't be of anymore help, but i thought i should give you this advice :\