I use a free weight bar, the same width as the big olympic bar (6ft is it?) but its small size thickness if you see what I mean. I don't use the Olympic weight, just standard plates and I never count the weight of the bar itself.
I find the wider the bar the better/easier it is to press and I also like using the loympic bench down our gym as it has a wide bit to lay on. Some of the other bences are thin and dig right in to my shoulder blades.