Depends on the service you stream to. If you're going to Twitch, 6000kbps is still not enough for 900p60 video. Even the well-known over-rate rate still isn't enough... and running at 6000 or higher is a terrible idea anyway as far as stream accessibility goes; you'll shut out a LARGE part of your potential viewer pool unless you get transcodes (lower quality options) enabled, which isn't reliable for anyone but Partners.
Better advice would be 'don't get lost chasing numbers'. Very few people will fullscreen your stream, and the pop-in standard window with chat open is around 720p anyway. Far more important is having good audio quality, levels, and balance between your game and microphone. Many will leave your stream open in the background, many not even watching the video at all, just background noise.
