The only bad advice around here is yours.
He is not entirely wrong or right, I guess his reply was cause op is inexperienced so he will never hit the consumption you would hit. I do have experience and I can say 1000w is more than enough but you need skill to optimize it. Also the prices you said are spot on, around 2100 usd, 5 x rx 580 will give you around $4 per day which in turn you will get back your money back in 525 days or 18 months to be precise but your system will have to be 24/7 and without problems and that is impossible, so count it as 24 months to get your money back. If you buy eth right now, in few days you will get 500% or more hehe and no problems at all.
I am not against overbuying on a quality PSU, well I am to a point, but linking some benchmark showing some extreme wattage usage does not help a beginner in any way and that was the main point to my rebuttal. Also, I think if you are getting into mining you do need to also learn how to tweak and optimize your rigs. Just throwing an overpriced excessive wattage PSU at non-optimized settings may have worked in April, May, June, July, and perhaps August for ROI purposes, but going forward people getting into the game are going to need to learn to optimize, optimize, optimize.
As far as the ROI question, I am with you 100% but I am tired of pointing out the obvious to people who only want to know how to get into mining. So I stopped pointing that fact out and now just offer advice on how to build rigs. But this again empathizes my goal of not overspending where you do not need to. Spending an extra $50-$75 on a oversized PSU will only lengthen that period.
So I recommend to the OP once he buys his gear, which I stand behind in my listing above, that he also comes back and asks about how to tweak it for optimal performance. There is also no harm in buying the base components that will support a a 5-6 GPU rig and only starting with 3-4 GPUs to learn these intricacies. Once you have this down you can always upgrade your rig to its maximum potential. This way you will have the best of both worlds, a reasonably priced and sized rig and you wont burn your house down in the interim period of learning how it all goes together and works.
theres one problem with your "but going forward people getting into the game are going to need to learn to optimize, optimize, optimize."
garenteed that's going to be too much for a beginner to handle and not to mention ANY BIOS MODS VOID THE FUCKING WARRENTY, which might I add YOU DIDNT MENTION. come on man. how would you like to be told only a part of the information then only to find out the gpu someone else told you to mod got screwed and they failed to say hey if you mod the bios it will void the warrenty and you wont be able to get a replacement unless you can manage to get the original bios back on it and also considering most gpus currently only come with a single bios telling a noob to mod his stuff is in fact a bad idea all in itself.