randynealpetersen:
Would you recommend something like this?
SainSmart | Desktop CNC, 3D Printing & DIY Tools | Power to the Makers – SainSmart.comor making it yourself? If so, what components should I buy?
The channels on the module can only handle 2A each. That's 220W and 110V. Won't work for your 400W load. For a 110V 400W load you want a 4A (440W) or higher capacity.
If you are only controlling one heater then a single SSR should work fine. DigiKey.com and Mouser.com are good sources of components.