My opinion, you want at least 75 watts, up to around 150 watts+, with a 4 12 cabinet that should do anything you want for a long time.
Things to look for, how many lines out does it have in the back. I would look for one with at least 2. So if you ever want to add another 4x12 cabinet all you would have to buy is a speaker cabinet and a cord. If it only has one line out does it have the power to run 2 12 cabinets in series. How many instruments can be plugged in at one time? Do they sell a cover to cover it during transportation? Does it have a switch to change the ohms it puts out to run speakers with different ohms? Does the head have a stand by switch?
The speakers in the cabinet are also a big part of the sound. As long as the ohms are the same, there is no reason you can't run one kind of head and another kind of speaker box. Best of both worlds kind of thing. For the kind of money you’re talking about spending Do Not Settle. If you can’t find something that speaks to your insides go to another store.
When listing to the setups, stand in front of the amp and back at least 8 feet. There is a wall of sound waves moving from an amp that big you want to be in front of it to feel it.
I would buy a brand that has been around for a while as far as the amp goes, but you will have to decide on what brand. Play through them all, no one else’s opinion matters, but yours.