A lot of things can be fixed w/alterations by a good tailor, but the quality of material and general fit will still be lacking.

If you're in Utah County, I've been really impressed by Perfectly Suited by Garth (downtown Provo, near the City Center Temple). I'd also second the recommendations for Indochino.

If you do go ahead with Mr. Mac, consider budgeting an additional $40 or so to take it to a tailor and have them alter it to fit you. You want to avoid the boxy, baggy, limply-hanging 2nd counselor look at all costs...