Ok so I know PH is important to keep stable but how important is it to get it in the ideal range? I currently have a Mixed Malawi Tank and it has been up and running great for 3 years and I have always added a PH buffer when changing water to get my PH up to about 8.4. My PH out of the tap is about 7.5 and I already have very hard water here so is this really necessary for me to add the PH buffer? I didnÃ¢â‚¬â„¢t know if I have been throwing money down the drain or are there actual noticeable differences to the fish behavior/health?
In my opinion, it's over emphasized. To a certain degree, stability is more important than it being ideal. In your case, a stable 7.5 would be fine. If you're using a store bought buffer and you still want to buffer use baking soda to save some $$.
Would crushed coral raise the pH for you. It would after all be a one time purchase if you really want a pH over 8. Like all hobbies it is designed to each up the dollar especially when you don't know.
As long as the KH is high enough to maintain the pH, which sounds like it is, then I would stick with your plan to gradually wean them off of the buffers. Why create more work and risk of mistakes if you don't need to?