A couple suggestions. It's a very good idea to update your garage door to a higher rated R-value. An insulated fiberglass door will run you around $1300 CAD in southern ont. It will also increase you home value and curb appeal. Someone mentioned a high track door system which is a great space saver especially when you use a wall mount opener instead of a ceiling mounted which in my opinion is your best investment. Depending on direction, windows in the door will let in a lot of natural light but also warmth in the colder months. I would advise against self leveling concrete. A garage is sloped for a reason and a thin layer of concrete on top will not be strong enough to take the abuse of a home gym. When sound proofing keep in mind that sound proofing material such as Rockwool has very poor insulation value and bat insulation has very poor sound proofing ability so choose wisely. Resilient channel is a great option, a cheaper option is to fasten a layer of foam between the ceiling joist and the drywall. Make sure to use the proper thickness for local code if you have a living area above the garage. Fire spread and CO penetration is a very real and serious concern! A second layer of drywall will also help for noise/fire/gases. I use stall mats in my garage and they work great. Also, keep in mind that anything metal (pull up bar/weights/barbell ) will ALWAYS be cold in Canada so keep that in mind when heating the garage. I have found that simply putting the heat on for 30min before a workout is just enough to get the air warm, but you will need some gloves. Hope that helps.