LEDs don't generate the same heat as halogen bulbs, and therefore don't require hoods for that reason. However, I was in the same position as yourself and put hoods on them for heat retention purposes. I.e. I didn't want the heat going from the room to the attic through what was in effect 9 holes in the ceiling.
The hoods I got were specific fire-retardant ones. I got them online, can't remember where, but they aren't too expensive.
They would not be any good for the speakers as they looked like fibreboard, and would probably deaden the sound (you want a hard box for the speakerboxes). One option to consider, for the speakers, is plant pots, ceramic, earthenware or otherwise.
Please note I'm not an electrician, just did some personal investigation.