>> i'll use Box mounted RCA jacks, not the PC mounted, so i have to be careful to insulate RCA ground from chassis, isn't it??
Most good quality jacks come with plastic or teflon washers just for this purpose.
>> the box is "white-PC-horrible-painted" so i planned to buy spray paint. Do i have to get any consideration about kind of paint or something else??
Any type of paint should do.