with 30# already in youre probs fine. It's just about getting it to look nice and have good places for coral to go. It's tempting in the beginning to fill up the tank but try to think of the coral as the last piece of your aquascape.
For me as long as theres enough spots for fish to sleep and it looks good, that's all you need. You an grow enough bacteria to process all your tank's ammonia on pretty minimal rocks, the extra in the sump can just cause problems by trapping all the poop that lands there. Like after a certain amount it's actually working against you. I disagree with the whole more is merrier position on rock. You see a lot of threads where people have their sumps chock full of sand and rock and algae, and they are fighting nitrates.
[unless youre trying to grow pods for a mandarin, then some rock piles are good pod-condos, you just have to clean up after them]