i bought mine from ebay. Sellers name is acrylic master. rated for 150 gallons for about 170 shipped. Too bad they no longer sell online. The next one would be home made using a sterilite plastic cabinet and a 30G tank.
I have done both. I have used Amiracle, Tidepool, and home made using Poly tanks. It really depends on your skills and needs. For a small aquarium of up to a 150 gallon FW, go with a large WD. Larger than that think about a DIY plan.
amiracle is good...I am using it right now but I just custom made one today with a 50 gallon acriylic and a broken acrylic canopy. I will post pics when everything is done I still need to get those white crates and silicone.