I like SBreeflight, which is actually really good quality for a good price. They have the 36" fixture ~350W for your 55 gallon for like $300, (cheaper without a built in timer but a timer is very useful). Located in Florida.
If you care about the plastic divider in the middle of your tank, blocking the light in the center and creating a shadow, then two ocean revive t247, $180 each on amazon are pretty good. These are less powerful than the SBreeflight, at 120W each, so actually cost more overall, but would have better spread and full heat sinks.
As for any of those other "black box" fixtures such as viparspectra, on Amazon for ~$100, they are not really full spectrum, and have too much white (which are probably just 6K and 10K, more suited for freshwater or plants), which makes them a bit less useful in the long run when you're really getting into your corals and will want to upgrade them anyway. These basic "black boxes" are entry level, and you'll end up running the blues (which are probably just the 450nm) at 100% with white at like 25%, which is wasting half the fixture's capacity.
You could replace half of the white channels LEDs if you can solder, but with all that effort, might as well get a full spectrum, color enhancing fixture, with blues at 420, 450, 470nm, whites at 10K and 12K, and they even throw in a single red 660nm and green LED per side.