I have a magnum 350 pro system and a seaclone 150 on my 125 gallon reef. I have about 100 lbs of live rock and a 2 inch sand bed. You should tell us if you plan to do fish only or a reef. Bioload and a ton of other factors will decide how you go.
Personally I would just use LR as your bio-filter. A sump IMO is a good idea. It will help in oxigen exchange, it gives you a place to dripping kalk, put your heater and skimmer, etc... Just my 2c.