One thing you can do is wait until the end of the season when everything's on sale. Springtime is usually the worst time to buy a bike, and we're in a bike shortage right now to boot. I don't think anybody's going to discount a decent bike. The brands you mention are all reputable.
A few years ago I bought a new bike in the spring, but I figured that a summer of fun was worth paying a bit more for the bike. Sure enough, the store marked it down in the fall, but I have no regrets. Right now I'd pay it to get some exercise, blow off steam, and avoid the covid.
Diamondback, Raleigh, and Fuji are interesting brands that seem to have somewhat different dealer networks, and occasionally good prices. I'm quite happy with my Diamondback. They seem to save a few dollars by using a reasonable mixture of brand-name and generic parts.
Below that $400 level (give or take), you may have to do more of the quality control yourself, such as checking the tension of the spokes and lubrication of the bearings. At the same time, gaining at least some basic bike maintenance skill greatly improves the practicality and enjoyment of cycling.