+1 It helps an AWFUL LOT. Running carbon 24/7 helps to polish your water from the yellowing toxins that corals produce, fish waste, etc. Using a reactor is the ONLY way to successfully run carbon or GFO. A reactor runs the media 'actively' as opposed to 'passively' in a media bag. In a media bag, water wants to flow around it as opposed to through it (dynamics of water 101). In a reactor, a pump forces water through the media. Much more efficient.
I would recommend a reactor for GFO and carbon. GFO for controlling phosphate. And carbon helps with GFO with bacteria along polishing water. As long water runs through GFO and carbon.
+1 on carbon and gfo you can run them inline with your existing return pump if its strong enough i have 2 of the brs reactors they can be tuned individually as opposed to the dual reactor