Hey! Once you've reached 1560 Power Level (without Artifact levels), that's the highest your armor will get you to; your artifact is the only source of additional levels now. Personally, I think 1580 is a fairly good spot to be regarding high level content, such as Master Raids and higher difficulty Nightfalls. It's past the cap for Grandmasters (1575) and is at the level of any Master content (1580). Though, going higher will allow you to get a level advantage on opponents in the Master content.