I just bought a house a few months ago with a 22x22 detached garage. Walls are 2x4 as well, i used r-13 insulation and 1/2" drywall and it cost about $300 for the materials.
I bought one a few months ago and have no regrets, use it almost daily at work. I was going to try the IR IQV one but couldnt find any reviews on it, being so new to the market.
Mine flicker and humm in the cold weather till they warm up as well, normal for the older flourescents. They make cold start lights that dont make any noise or flicker when turned on down to 0 degrees i belive.
Hinted around to the wife yesterday that they were on sale. She called me from work and said to go pick it up after work and that it was my christmas present. :)
I found a good deal on a Modine PA75, only problem is it's natural gas and i have propane. Can it be converted to work with propane? I've searched but haven't come up with much info.