Watt Density

What does everone consider Ultra Low Watt Density? I see alot of hot water heaters are running about 50 Watts PSI or so. I want to do a recirculating mash through a rims tube. The heat stick i have is 500W with a wat density of 6.06 No scortching at all but can not keep my mash at temp if it is below 85 outside. I am thinking of jumping up to a 2000W heat stick and adding extra insulation. The 2000W heater I am looking at is 3/4" by 38" with a watt density of 22.338.

Will this scorch wort?
Will it carmalize wort?
Is this enough watts to keep my mash at temp with the ability to do a mash out? I use a converted 15 gallon keg for mash. it is insulated.

What is the range of watt density recommended for beer? (w/m2)

I haven't used a 2k in mashing but I thinking the scorching issue comes from people not cleaning their elements between batches, to be honest.

You didn't say what size batches you do? 5? 10? How much power is available? 120V or 240V?