i would get any old 20g tank (or what ever you can fit under the stand) and make it into a sump or better yet if you use a HOB skimmer and dont mind the look of it in the display tank the skimmer along with your live rock will take care of all the filtration.... no need for a wet dry but its nice to have a sump 1. to add more water volume and 2. to hide all heaters, skimmer, ect...