Regular home computer? With my kind of rig, doing those kind of tasks are like walking in the park. All with a budget of $400-500.
Your intention is like using a sports car with an average speed of a mini SUV. It would be a waste of money and power.
Think of it as a closet. If you want to put only a few things in it, get a smaller one. But if not, or if you intend to fill more things in the future, go for the bigger one
My advice, since you're application aim is clear, go for the "Green" concept.
But in the end, it's all up to you