generally, you want your pump to give you 5-10x turnover on your tank. (so for a 46g tank, you will want 230-460gph)
5x turnover is pretty standard. if you have an "overstocked" tank, or fish with a higher bio-load, you may want to go higher. also, a higher flow rate will help increase mechanical filtration in your sump.
keep in mind that with the pump, you will have to factor in "pump head". depending how tall your stand is, you will need a slightly bigger pump. (if your 230GPH pump sits 3-4 feet under the display, it will probably only be pumping around 150gph). most pumps will have a chart on the side that shows you the GPH of the pump based on different head heights.
the other thing to factor in is your stock. while some fish would be happy even in 100x turnover, some are easily stressed by high flowrates (like bettas for example. they dont like too much water movement)
as far as the filtration itself, you cant really "overdo it", but if your fish are not happy, then it may be too much. as long as you dont have easily stressed fish, you will be fine.