I don't think denon & onkyo have such features .The mic hole u might have seen is for ear phones only.
Earlier Philips ,sony & samsung DVD HTiB models used to offer this Karaoke feature.Now it will be rare.
I'm using a Pioneer DV-3032-DVD player in which karaoke feature is there.U may need to buy a seperate mic for this .This DVD player can be connected to your Hometheatre setup .
But the total budget may shoot up 30k.