Maybe it's just me, but i am somewhat confused by your question. If you are looking into getting an aqaurium with a built-in overflow versus an external set-up, depending upon the aqaurium manufacturer and who you buy it form, alot of times all of the plumbing; intake/strainer, bulkheads and drainpipes etc., may already come assembled, and installed. If you are getting one without the plumbing, get one with pre-drilled holes that will match the dimensions of the kit you are planning to buy. You want to avoid having to have an aqaurium drilled if you can. Most aqauriums have tempered glass for the bottom plate. This glass requires diamond drills, and a very steady hand. If you need holes drilled call around to glass shops to see if they will drill and aqaurium with tempered glass (be ware most will not pay to repair the glass if it cracks - which is easy with tempered glass). If you are determined to drill youself, there are drilling
DIY's on the net as well as threads within fishlore about this, and all of the pro's and con's about it. As to the sump, the overflow kit you show has a rating for 600gph, so you want to match up the return pump to your drain rate obviuosly - but, the 600gph is max, there will be media in your sump and restrictions from the hose connecting the aqaurium to the sump, so you will have a something less than 600
GPH. For a 30g aqaurium, i personaly woudn't want a return of 500-600gph blowing back into the aqaurium - you could either look at reducing the flow in/out of the sump by reducers/smaller pump 200-300gph?. just my opinion for waht it is worth, i would at least diffuse the return via spray bar or variuos outlets otherwise a large voulme of water for a 30g.
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