FWIW, I've never used heated socks or pant liners nor found them needed down into the low 20's. Keep your core toasty with the jacket and hands warm with grips/hippo hands or heated gloves and being cold isn't a problem.
Save your extra watts for lights and other goodies you didn't know you needed!
--G
Same here. I've run my ZRX (very little wind protection) into the teens with just the jacket liner and gloves. I wore a pair of insulated First Gear pants and thick socks in my regular riding boots. My legs and feet got chilly, but I wasn't that uncomfortable.
FWIW, a friend does have the electric socks with his, and he says they're very uncomfortable for walking. That's second-hand info and maybe worth what it cost, but the guy's an old hand at riding and usually has good info.