Well first of all, good for you for doing research before hand! Lets just say you have come to the biggest source of ball python reading material right here on this forum!
Since you are getting a baby snake, I would go with a smaller tank. If you don't feel like getting another bulky tank, I would think about using rubbermaid tubs. They are easy to clean, easy to heat and easy to keep humidity in, especially with winter coming up.
Make sure whatever hides you get are TIGHT fitting. The snake should barely fit inside. My snakes don't even fit in their hides anymore. They just wear them as hats.
Go with belly heat, that means an under tank heater. CHEs and lamps will suck the humidity from the air and makes it near impossible to get to acceptable levels.
The catch with the UTH is that you absolutely need a thermostat. You can kind of get away with without one if you use lamps but there is still a risk of thermal burns. Thermostats range in cost from the cheapest model at $20 to the most expensive at well over $100. The reptitemp 500r should suit your needs.
You will also need to closely monitor the temps in the enclosure. This can be easily done with the accurite weather station. It can be found for around $12 at lowes, home depot, and walmart. It measure humidity and has two temperature sensors. One sensor is an external probe that you will place in the enclosure with the snake right over where the UTH is under the substrate.
Contrary to popular belief, you don't really need a soaking bowl. Ball pythons do not normally soak and if they do its usually a sign of mites or a husbandry error. So you don't really have to get a gigantic bowl. I use 4" diameter bowls and they work just fine...although I probably need heavier ones because my snakes like to tip their bowls all the time :/ ugh!
Feeding in a separate enclosure really has no benefits. Many snakes will not even eat in a separate enclosure because they don't feel safe. Feeding in the enclosure will not cause cage aggression since you will be going into the cage to do other things throughout the week other than feeding. I feed all of my snakes in their enclosures and I have never been bit (never say never!! I will probably get bit today or something D.
So here is a new shopping list:
8-15qt tub for a baby snake-----------------$10
10g UTH------------------------------------------$20
Reptitemp 500r thermostat------------------$25
Two identical hides----------------------------$20
Water bowl-------------------------------------$5
Accurite thermometer/hygrometer---------$12
You could probably be creative and cut costs a bit more. Check out the dollar store for small opaque bowls that you could use as hides or for crock bowls that you could use as a water bowl.
Good luck
Oh yeah, the Pythons of the World, Vol 2 from VPI is simply AWESOME. I will eventually buy one just because it is soooo wonderful.