Hey dude, welcome to the forum.
Speaking from personal experience, which incidentally seems to be following a similar path to yours, you seem to have the right ideas about nailing your tone.
When i started, i had a jackson guitar, and an MG30 too. one regret i had at the time was rushing and buying an amp i could afford rather than buying the amp that i wanted. This will only mean that you will need to buy another amp later. Any valve/tube amp will help you get the best out of your sound, even something as small as an orange tiny terror or any sub 15watt tube amp will deliver the goods and power any speakers you hook up to it.
This is the first step i would take. Once you have done this i would definitely look at a crawler, rebel yell, a riff raff or an emerald as all the arists you mention don't use crushing gain, just varying degrees of crunch, even system of a down don't use thick 'metal' dist, but punkier crunch gain. This is why i feel that the progressive high gainer might bee too much for you. I have a crawler and it meets all the metal needs i have, and my taste seems similar to yours. I also have a nailbomb and i think it might be too much for what you need it for.
However, go to a guitar shop, and get someone to crank some cheap tube amps for you, you'll need it one day, and you'll never regret it.