Hello, I'm new at this so please be gentle, I'm a master plumber and have done new construction for twelve years. I have very little drain cleaning experience. The advice I recieved on my first post was very helpful but now I need more advice. Looking at the Ridgid website I see the K380 and K3800 are similar except for price, also the K750 and K7500. Any suggestions for the best choice to begin my new adventure ?