If you’ve got a spacious case, yes. If you haven’t, then you want a modular PSU, so you only have the cables that you need, and you want cables that are as short as is necessary. You also want cable ties to secure the cables. Lots of cable ties.
Seconded. I bought one about two years ago, and I don’t think I will ever need to buy another case. Expensive, but worth it. It’s also designed to be as quiet as possible. That was my main motivation in buying it. Everything has rubber seals, and the sides have foam insulation. My only complaint is that it is just enormous. It looks like you could put any other case inside of it. Check the specs, and make sure you’ve got room.
ETA: it even comes with tools, tons of screws, and cable ties
Just to join the chorus here - everything in a PC runs on electricity and almost everything is very precisely engineered to run at particular voltages etc. A decent PSU provides all those components with a nice steady well-regulated diet of electrons prepared in just the right way for each component. You simply would not believe the weird symptoms and expensive failures that a crappy power supply can cause.
Having said that, don’t mistake marketing watts for real watts. A decent-quality well-made 400watt PSU may provide better results than a crappy chrome-plated 1000w job that sounds like a jet engine and is primarily designed to lighten your wallet. Seasonic, Enermax, Antec, and Corsair seem to be well-regarded, but look for something with a decent efficiency rating and then google for user reviews. And modular PSUs are just awesome for simplifying the inside of your case - just make sure you figure out which cables you will need and plug them all in BEFORE you put everything into the case.