Do you really mean 66 and not 76 degrees?
Do you sleep with a couple of quilts on?
We just had central AC put in our small house, and leave it at 77 during the day, if at home. If we go out and at night it gets set at 78 degrees, Humidity stays between 52 -56%

Before getting a wall unit, I would see if I could balance the air flow, by either closing some registers a bit, or installing dampers in the colder rooms and maybe a larger duct to the warm room. Wall units are loud! One of the reasons we finally got central.
Before we had a 16,000 BTU wall shaker, which required fans to distribute the air somewhat. LR where unit was, was noisy and chilly!
After putting in the new AC, July 2014 elec bill was $102. July 2013 elec bill was $143! Plus, we are much more comfortable now.

66, with a light blanket. Just like my son.
We cannot sleep well when we are too warm.
All the doctors and sleep experts recommend 66.

Balancing air flow, we already did everything we could with that.

Thanks.

We have a cheap window air conditioner that we install for the summer and have it set at 60 but then we do live in Canada and it gets hot outdoors( 35*C) but we like it cool at night too. If you install it in a bedroom say across the hall, it would or should be close enough that the noise would not bother you but still cool it to 66 * f . Ours is one from Sears( Kenmore ) and paid under $200 and have been using it for over 5 years in the summers and that is almost for 3 months each season. We pop it out and store in a shed for the rest of the year so no drafts coming in from outdoors when not in use.

opps, double posting.

This post was edited by almosthooked on Wed, Aug 6, 14 at 16:49

Unfortunately, we sleep with the door closed, so an across the hall unit would not help.

It could go in the closet, which is always half open. That might hide some of the sound.

What have you done to change air flow? If your coldest rooms don't have ac registers right off the supply plenum, (as I do) You should be able to increase the warm rooms duct/register, and restrict the coldest rooms.
I'm dealing with our spare bedroom, which we don't go in much at all, having a supply register, right off the supply plenum. Talk about a cold room. I removed the register, and installed a baffle, to block off 1/2 of the flow. The room is still much colder than others. I installed another baffle in our bedroom supply. It is off the supply plenum at the far end.
I'm doing this on my own, after kicking the installer out of my house. That's another story.
I don't want to block too much supply flow, as this upsets the static pressures, and could cause problems.
After the cool season, I am going to block more of the 2 cold registers, and also running a new branch to the main area of the house.
When it was designed, I had the installer add an extra return duct. I head that a lack of enough return can be a problem. I had wanted an extra supply register. Which would make the total CFM, more than desireible. MY plan was to always having some of the dampers closed. I would be able to close 1 totally, and still have proper cfm. I could close 2 damers 1/2 each, and be fine. I discribed this to 2 salesmen that gave me qoutes, but they all said it wasn't needed. Seemed like a good idea to me.

Anyhow, Give more thought about balancing the airflow. I mean, isn't that the problem?

. For now, we shut that return, and leave the louvered door to that room opened, so the cold air has to come out of the room, and go thru the LR, past the thermostat, into an open room, to the main return.
Still colder in that room.

You might check out Friedrich for a window or wall AC. They've got a good reputation.