In general, it seems to me that today it's all easy, because there are a huge number of services, sites and other opportunities that allow you to solve all the pressing problems and find any goods, services, etc. that you need. And of course you should pay special attention to the quality of what you use and of course the feedback of real people who have already tried this or that. And it's really cool opportunities, which have become for all of us the stage where our problems have become much easier to solve, and we do have almost unlimited opportunities and that's what inspires me the most in the twenty-first century.
The problem that I've run into with older cases are limitations with the Motherboard in terms of expansions and updates. The power supplies get bad as well. I was able to get that Tower from the Lenovo Factory Outlet cheaper than I could get the components from NewEgg: Tower Case, big enough power supply for multiple HDD's, MB, CPU, Video Card, HDD, ethernet card, sound card, and OS-10 64bit. And it came with a full factory warranty and some above average diagnostics/maintenance software from Lenovo. And for something like $225 I bought another 4TB HDD and more memory from NewEgg.
Ebay has been and remains a much needed resource that allows you to find and purchase everything you need. And it really erases the boundaries between countries and continents. I remember when it first came out and how it was unexpected and people were only buying small things there, and now it's already a common resource that's in demand and that allows you to buy large quantities of goods, plus it's where you can sometimes find what you need at a more affordable price. And I like the auction system. So I would probably be able to recommend it to my friends or acquaintances, and it can definitely be a real help in business matters. And it's true, you can find absolutely everything here!
I'm not as tech savy as you so I just build & buy with Lenovo. I like that they offer a warranty plan where they service your computer at your home. I have used this service and it is excellent! I have a thinkstation mini at home with 2 screens and use lenovo laptop for non-trading stuff or when I travel. I'm a fan of the factory outlet!