stereo cuts out at med to high volume

when i am listening to my stereo, it cuts out at any volume level above mid way. my front driver speaker was gone so i replaced the front speakers with aftermarket and bass blockers and still have the problem. i cant get it repaired by factory techs bc i have added an amp and sub to the system so they will not honor the warranty on it. any ideas?

Warranty just means they fix it for you for free, spend some cash and get it fixed, sounds like your head unit might be fuggled.