If you are looking to invest the money in a pied baby {excellent choice by the way} you are going to want the best possible set up for the baby to make the transition to your home go as smoothly as possible.
Not to mention, proper care and good feeding means a big, healthy happy snake.
I highly recommend reviewing the caresheet here :http://ball-pythons.net/forums/showt...s%29-Caresheet
As far as belly heat, you might possibly be thinking of heat rocks, which are a very big no-no.
A properly regulated UTH mat is an excellent choice for a ball python, as they really do better with belly heat to properly digest their food.
Aquariums are a great deal of work to make suitable, but with persistence it can be done. I know tubs are much less aesthetically pleasing, I struggled with that for a very long time before I conceded tubs were the way to go as my collection grew. With only one snake to focus on, you can do it if you try.
Gale