i currently have a ps3 connected to jvc 56" 720p TV thru regular hdmi cable and i'd like to know is it worth connecting with hdmi 1.3 cable even if tv doesnt support that standard.

If your current HDMI cable doesn't give you any problem, don't waste your money. It won't improve anything even if you buy a pure gold cable :) Unlike analog cables, HDMI is pure digital, if it works, it works.