A mag 7 is definately not enough flow IMO. Since your budget is small but your sump is descent size for that size tank I would recommend replacing the mag with a rio hyperflow 32 or a quietone 5000 or 6000. All of these pumps are cheap and then you could invest in an exterior overflow if you do not want to drill. If your returns are in the corners I would recommend penductors rather than lock line due to the water movement that they produce. I personally hate the look of powerheads but if you are going to run one or two I would go with Seio's. Tunze are awesome but they cost a preety penny and the Seio's are the next best thing for about half of the cost. You could also do a closed loop and keep the mag seven but that would involve a descent amount of drilling. If you were to do a closed loop I would again recommend a quiteone pump like a 3000 or 4000 for that application (I do think this would be a little over the top for this style tank). As I am sure you will find there are an enormous amount of opinions out there on optimal setups and most of them will work just fine. I would really think about what you want to keep in your tank to help assist you in your build.... To summarize, if it were my tank I would get an internal over flow form someone like socal creations (three sided so it's not so deep), silicone it in, drill two 1" drains for durso style drain pipes, drill 1 -1" hole in there for a return, drill two 1" inch return ports near the bottom of the overflow enclosure (about 5 inches up off the sand), drill two more 1" returns about 4" from the top in the overflow on each side and "t" them all off of each other. That would maximize the space and hide all of the plumbing work and provide awesome watermovement. I did a similar thing on a 55 tall for a friend of mine and it is awesome ! If you want me to draw a diagram of plumbing, overflow desing let me know