bag upgrade

i want to upgrade from my 1/4 firestone bag to a new bag with a 1/2 port any ideas? i was hoping to find maybe something that will make it lay alil lower also..was it firestone or slams that have the new ones that compress the most

also ive read on this camaro forum that different brand of 3/8 valves can out perform eachother is that true? i figured 3/8s is 3/8s