Sears still has good warranty. Buy the latest version of C3 and if you find it does not work for you, return it within 30 days. I am happy with my older C3 once I got lithium battery and charger for it.
If you use straight impact socket on it, there is no problem in taking off lug nut at all. If you start using extensions, converters or non-impact rated sockets, then you will have problem getting the full output to the fastener.
This topic comes up every few months here. If you search, you will find few of us have C3 and are happy with it. I also have smaller DeWalt and frankly, I find I use it lot more often than the big C3. Ergonomics play a big role in an impact wrench and DeWalt 12VMax line delivers. It is just phenomenal when working under the hood or under the dash. But the bottom line is, it is pure luxury to have them and definitely not something you need it as a home wrencher. There are probably lot of other tools that you may realize are needed in your toolbag than cordless impact wrench(es). One thing is certain; once you have a good one or two, you would be wondering why didn't I buy it earlier!
Having said that, if I were in the market today for a cordless impact, it would be M18 Fuel High Torque! But that will not fit inside the budget given in the original posting.