Welcome to the forum!

The shocks you have now are very good and the only way of getting better shock action is to do the LST shock mod. For this you need a special kit and 4 lst shocks and your set. As for the oil your using its way to thick, i run 25wt in all my shocks and its just fine for me. 600 to 800 is much to thick, get something between 25 and 40 to replace it or you will bend the shock shafts when landing a big jump or hitting a bump.