Bottom heat won't help them any more than an appropriate ambient temperature. Temps in at least the high teens is what they need, but, more importantly, as much bright natural light as they can get.
My toms are all planted out now, but, a month or so ago, I had them in my small portable plastic greenhouse on the terrace during the day. It was sunny but cool, and even with the door open the plastic trapped enough warmth to satisfy them. The light, though, was the key. They boomed. I brought them inside overnight.
Peppers simply take longer than toms in every way, shape and form. With the toms already planted out, my peppers - germinated at exactly the same time - are still only about 2 inches high.