Toxik was a prog/thrash band from Florida of the late 80s. They were on Roadrunner if memory serves. I only have a CD-R.
I can't remember what their debut was called but it's not as good as their second, and final, album "Think This". I'm tempted to say that they sound like a more straightforward Watchtower but that description isn't really fair because they had a sound entirely their own. I guess I just mean that the description holds true inasmuch as the vocals are high (dude has a REALLY good voice - maybe my favorite of all the really high metal singers), the guitars are fast, and the music is more thrashy than power metal. They aren't as wacky and humorous as 'Tower nor are they ever as dissonant but they do get surprisingly fast for they type of band that they are. Usually the tech/prog bands with clean vocals from the 80s don't even approach Slayer tempi but Toxik will occasionally play about that fast. I don't know what else to say about them really. They totally rule and from what I know about your tastes, you'd probably not regret going to Vintage Vinyl (a friend of mine found an LP of it there; maybe they have it on CD too) or looking on Ebay and just buying the album. It's a damn shame that they've been so overlooked.