The amount of water changes you need directly reflects the amount of filtration you need. The more filtration you need, the
more often you need to do water changes. If you have enough fish, or types of fish, that require a lot of filtration, then nitrates will build up that much more quickly and water changes will need to be done that much sooner. Plus, as nitrites are turned into nitrates hydrogen ions are released, and this process steadily brings the PH down, therefor the the more nitrites that are converted, the faster the PH drops, and the more important it becomes to do water changes to keep things level.
On the other hand, you can add all the filtration you want to your existing setup and it will not change how often or much you should do your water changes at all, because the bio-filter will still be exactly the same size, only it will be spread amongst a bunch of filters instead of just one.
I use an Eheim myself, you cant even buy bio-wheels here but I think if I could get one, I would.
You only, only have biological filtration problems if toxins are testing positive. If you have no trace of ammonia or nitrates in your tank then
you do not need any more biological filtration. period.
In my opinion nothing, not filtration, not anything, is more important to a fishes well being then water changes, and if I could afford it I would run my aquariums on a continuous fresh water flow and have no filter at all.