hello guys

i have a canon 70-300mm L IS and a 400mm F5.6 prime and the camera is a canon 7d

i would like to buy a tamron 100-400 because the 400mm prime is not very convenient but i was also wondering maybe just to buy another camera i'm not sure what camera i was thinking the 77d but maybe it would be best to get a full frame? like the 6d or the 5d mark II i don't know whats best so i was wondering what you guys think ?

i know the tamron for canon has the same image quality as the 300mm even when it's at 400mm

or any other options like the canon 100-400 mark I or a different camera i'm really looking for convenience

so tell me what you guys think thanks in advance