DYI UGH, any opinions?

I am setting up a 75 gallon heavily planted tank.  I've read about the 
virtues of rootzone heating (both in the aquarium and in the greenhouse) 
and am thinking of incorporating it into my setup.  I looked in the Park 
Seed Co. Wholsale catalog and came across heating cables and a thermostat 
to regulate them.  Park Seed says the cables are submersible.  Total cost 
such a set up in my tank approx. $50 plus shipping ($8 for the cables and 
$42 for the thermostat).  Any thoughts on this DYI UGH setup?

I'm also planning on planting my plants in undrained cut off yougart 
containers with composted cotton mill trash as the media topping off with 
sand and then burying this in a gravel bottom.  How's this sound?

Thanks for any advice.