Your GPU is pretty powerful and will have no problems playing 4K Material, especially as your LF6300 is only a 1080p TV. I don't know if you have manually modified your madVR settings, but MC also added some new HQ Profiles so you can just use those, and with a 1080 I'd say you could use Tools--> Options--> Video--> Load madVR quality preset--> High Quality (but not if you have mad any custom changes to madVR these will be reset).