They still need very large tanks. I would say a minum of 180 gallons. That will run you about 600 just for the tank. Not to mention the stand, canopy, lights, filters, and skimmers required for perfect water quality.
180 is still better than a 20,000gallon though so, it is doable at least. I would still direct your questions to the aggresive forum though. This forum is for the equipment needed for tanks and their DIY parts. The aggresive forum has many members who can better direct you in the picking of the shark..
Good Luck.