As for filtration I think it really depends on what you plan to house in your 150 gallon?
As for heaters, I would probably use dual 250W stealth heaters but I think you might be able to get away with one. Just nice to have two just in case one of them malfunctions.
Bringing back an old thread I'm in this situation right now, trying to set up a 150 gallon and don't want to drill it. I love emperor 400 filters but I have a silver Arowana I plan on keeping until it grows out as well as a Giraffe nose catfish and a RTC/SNC hybrid I want to grow out. Are HOB filters an option for this even if I did 4 with some bubbles to help move the water. What are your thoughts?