I'd go with the quieter fan approach. Get yourself some good Noctua or Scythe fans that run at 900-1200 rpm and you won't hear them but they'll move plenty of air.
While that will take care of the indside of the case, is your cabinet enclosed completely on the back, sides, top and bottom? If so, there's no place for the hot air to go. You may need to vent the back of your TV stand. You could cut a round hole and mount a 120 or 140 mm case fan on the cabinet itself and power it from the htpc so that it shuts off when the htpc shuts off, and that will get the hot air out of the cabinet. If the only opening is in the front, the hot air is just building up behind the htpc case with nowhere to go. This is especially true with most Silverstone cases which are designed to exhaust the hot air out the back.
And fanless PSUs are quiet but they still produce heat. If you are already having a problem exhausting heat, getting a fanless PSU isn't going to help your heat situation any.