radiant heat in basement
If you think about it, is there ever a person who says "Money is no object, I don't care what it costs...go ahead". You'd know that person by the line of contractors at his house stretching around the block.
Cost is always a concern, but I agree that being penny wise and pound foolish at this stage is a not a good idea. I'd bet 2" of foam would be even better, but that's where you get into cost/benefit analysis. $850 is probably chump change for the total cost of the project.....don't go cheap now.