I figure to save future problems, it's best I get one, right? Can someone recommend one that is somewhat affordable and reliable and what decent product should I get to create water flow in the 90 gallon tank but not put too much stress on the fish swimming?
The circulation pumps of choice are the EcoTech Marine Vortech pumps or the Tunze Turbelle Stream Controllable pumps. They are not inexpensive, but they will last almost forever, and you can get replacement parts. You would likely want two of them for a 90 gal tank.
If you want simple circulation pumps the Hydor Koralia Circulation and Wave pumps or the JBL Oceanstream Circulation pumps will work at a much lower cost, but be aware that they are not anywhere close to the EcoTech or Tunze pumps as far as creating random flow patterns in your tank.
With a few exceptions, fish are not usually bothered by the high flow as long as they have places where they can get away from it if they want. Some even seem to like the high flow and seem to ride on it.