I know for a fact the galapagos sharks at the Monterey Bay Aquarium have been particularly nasty to their tankmates - even pestering the great whites they occasionally get (up until they push too far... then... CHOMP). They also like to eat the tuna in there.
A scalloped hammerhead would be pretty cool, and sandbars just look badass.
I have to catch up with you this fall - my tank project has been headache after headache, and now with a couple product launches, I'm working 60+ hrs/week.
Sharkdealer's hooking me up with a whitetip soon though - the zebra fell through. Much like your Aussie sandbar - the shark itself wasn't too expensive... it was the $10K to ship it. And frankly, gas is going up, and my Lambo doesn't really sip gas...