It's a matter of finding balance. The fish need oxygen, the plants need oxygen, but the plants also need Co2. Too much agitation means less Co2.
I've seen very heavily stocked tanks (and I'm talking 60 fancy guppies in a 20 gallon) with only a HOB filter for water movement. Healthy fish, and vigorous plant growth. You don't a torrent going on.
The tanks I speak of, the guy does large water changes twice a week to maintain that fish load BTW. He breeds them.
You can use a canister on one end, and a power head throttled down a bit on the other, this will allow you fiddle with the current more.
Don't let me make you think that adding the second canister is a bad thing, if you end up stocking very heavily it could be of help to you.
I just wanted to point out that the plants themselves can be the ENTIRE filter in many cases.
Every tank is different.