Hi Chefwong,

I'm not really answering your question directly. But just thought I'd let you know that I've been using a "king size" sunbeam moist/dry heating pad (from Long's in my case) under my seedlings with great results. If you go this route, you may want to invest in an inexpensive instant read meat themometer to check on the soil temp in your seedling pots or trays and adjust your settings accordingly.

FWIW,
Anne

Like Anne, I take the inexpensive route - used waterbed heating mats. They have their own built in thermostat and thermometer probe. Find them for a couple of dollars at yard sales around here often.

The ones you linked to require you also buy the separate thermostat. Too expensive for me when there are much cheaper alternatives.

If I remember correctly you are only going to be starting a few plants, right? You can do that on top the fridge or the hot water heater or even with just a light bulb. There are many more suggestions for heat sources discussed over on the Growing from Seed forum. Save the $$ for soil amendments. ;)

Dave

I "third" the notion of the waterbed heating mat, which I have used successfully for 3 years now. I'm not sure what a "chrome variant" is... but its sounds expensive and unnecessary

I use my gas forced air furnace, the kind with floor vents. I put one of those cheapie web flats, the kind that have mesh for bottom and holes molded in the sides, upside down on the floor vent, then stack flats with germination domes on top of each other on top of it.
You can also use cookie cooling racks, bricks and cookie sheets, anything that lets the heat get out into the room as well as heat your flats. FREE! I get tomato seed germ. in three-four days usually.