Like @A Young reefer asked, what tank exactly. You mentioned a sump but also said AIO. AIO's are not truly the size they state which will limit space. Not all aquariums are made equally either. Skimmer chamber, refugium, filter area, return area... They can often dictate how you'll need to manage your tank. If it's going to be a centerpiece, plumbing, wiring, etc can weigh very heavily on what tank choices, stand choices and equipment choices you'll need to make.6foot x 14inch x 18 inch
sorry didnt reply earlier, i couldnt see your message somehow
Dreaming of the fish you'll keep is great, but I gureantee you your selection WILL change over time as you get more experience with the hobby. You're going to find out the difference between theory and reality. Knowing what a tang or angle fish's requirements are is not the same as having to accomodate them. It can become VERY tedious VERY quickly! You might find that you hate having to deal with certain fish or corals. Like, I don't think 20lb's of live rock is near close enough to give your animals places to hide or feel comfortable. In a 6' tank you'll probably be looking for much more rock. So, knowing exactly what tank you're thinking of will help people point out issues you may not be aware of.