I've seen a Powder Blue in a 75 before and it seemed to thrive. but, I'll do more research before. anywho, I won't be buying the 75gal before october. leves me alot of time to think things properly.Personally I'd shoot for a 100g + if you're wanting either of them.
but, my 30gal will definitely be converted into a sump. I've been reading/researching alot on sumps lately. think I can manage something decent with with the 30gal.