Personally, I like to use the hi-hats for lighting up the entire room as evenly as possible. Not every customer wants it it done like that, though. Some want them as you suggested - over the couches or whatever. And yes, recessed light manufactures like Halo or Juno do offer 6" "eyeball" trims for their lights. The eyeballs are obviously a little bit more expensive than a regular baffle trim.
As for the lights over the fireplace, I would go with 4" recessed cans with mini eyeballs and 50 watt par 20 lamps.
Good luck!
