Thermostat will be the best decision you make this year. I was waiting for my Herpstat 1 while it was on order and delayed. I had to change my dimmer 2-3 times a day. I had the opposite problem you have though I was too cool in my house. You will love not having to worry as much about temps. I still check daily (paranoid) but they are bang on even with A/C on etc. My house fluctuates a lot.
86 ambient seems really hot. Where a bouts are you living?
Please post how you got you ambients down for any future readers. I know that I stumbled across many threads with excellent advise given (like this one) but it is always nice to know the end result.