Another alternative I've considered is there's a computer store near the mall that primarily deals with business customers, but I have used them from time to time in the past, as when I once bought an external drive caddy to hold the hard drive from an earlier machine. I've thought about approaching them to see what they offer for custom built machines, though it would undoubtedly cost more. But I trust them, because they've treated me just as if I was as important as a business.
One reason I avoid Wal-Mart is I knew about them back around 1970, and how they would set up a store in a small town and drive the local businesses out of business (including my ex-wife's hometown). They used to be exclusively rural, but in the mid-70s they started getting closer to big cities. I really don't like going to them.