Video Card for MAC when editing RED footage in FCP

Just wondering if you need a video card, like the Kona 3 or others, for editing footage from the RED in FCP. I'll be working with the footage for the first time in a couple of days and I was told that you need a card to edit in Hi-res and also edit in Low-res without rendering. I heard without it you can only edit with Low-res, but you have to render and you can view the Hi-res files at all in FCP. But, I also heard you only need a card if you want to play back on a monitor. Just wondering which one is true or not. I want to have an easy workflow for this project. If anyone can help me that would be great. Thanks.