It looks like from the posts on here, that quite a few guys are building systems similar to Pols. It looks like a great system and I'm planning on starting a similar build myself. I saw that a Johnson a419 was used on his system to controll the hlt temperature. I was wondering what the difference was between the Johnson a419 and the Ranco ETC-111000? Will they work as perfect subistutes, or with your experience, is one a better choice than the other?