That Ingersoll Rand 231G is a pretty good common impact wrench. They are advertised at 500 ft.-lbs. of reverse torque. I would say that the deal you found at Lowes is a pretty good deal on a fairly good impact.
Here is another Ingersoll Rand Impact Wrench Model# 231HA it has Max. Reverse Torque of 600 ft. lbs. It is on sale at Northern Tool for $139.99.
The best High torque I have, bang for the buck, is a Ingersoll Rand Titanium Air Impact Wrench Model# 2135TiMAX. These are advertised at 780 ft. lbs. of torque. I like them because they are lighter. I have wrist troubles them being lighter makes a real difference by days end. You can usually find them for around $300. Have several MAC high torque impacts but they start at $500 and go up.
Some thing to remember Lanse is that these are rated at 175 PSI air supply and will use 20-25 CFMs while working. So if your air supply is at a lower PSI the torque will be lower than the rated torque. They will still out perform the one you had/have but will be less than what you may have used at a school shop or etc.
Also if your shop is unheated and you are going to be using them in real cold weather. Take them in the house and let them warm up an they will work better. When they are real cold they will freeze up when the cold air gets going through them.
Have fun the one you have listed would still be a big jump up for you and would make things fun to get apart. Just a little heat from your torch and hit it with your impact.