Glass cages makes a 65 gallon tank 48x18x17h for $165.00 . Plenty of room for a hug skimmer, large return chamber, media chamber, refugium, filter sock, ATO.
You might browse around this site - Lifereef Filter Systems I have bought a sump from them before and the quality of work is second to none. He has a long wating list though.
Your on the right track now! Problem is how big is your skimmer going to be? How big of a return pump? Start laying out your equipment list and make sure it all fits.
With that big of a tank you may wanna go with the first sump and add a refugium seperate and a auto top off tank seperate also. The possibilities are plentiful! Lol.
Would get you by for a while. But I'm sure you will want more flow at some point. I'm running about 1500 gph through my return into my tank and it's a 110g. But that being said I ran the tank through for 3 months with a 800 gph pump until I had the cash to upgrade.