I wouldn't say you *have* to have a sump for a 30G set up, but just remember - the more water volume the better off you are. Plus, you can use portions of a sump as a refugium (even more beneficial). If you decide NOT to have a sump, I would recommend more frequent water changes. As far as the live sand, there is a LS calculator (look to your left under the heading "useful information" and click on "calculators"). On the live rock issue - it's hard to say an average, as some LR weighs more than others (density). You would probably be OK with about 35lbs or so depending on the rock density. ;)

Wendy