You must be kidding.
Unfortunately, Cynic only made one album, called Focus. It's probably the greatest one album wonder in metal history. I'm surprised you haven't heard it, since it's absolutely essential for prog/death fans. Some Cynic members made the band Portal with a self-titled demo tape, but it was mediocre. Fortunately, they later formed the band Gordian Knot, which is an excellent instrumental prog band.
Cynic was originally a technical thrash band, so their early demos might be interesting from a historical point of view, but they're not essential. For great technical thrash, Watchtower is what you need. They only released two albums: Energetic Disassembly and Control And Resistance. They're both excellent.
From Atheist, get Piece Of Time and Unquestionable Presence. If you love those, you might like Elements, but only their first two are really, really good.
Coroner is more technical thrash. Everything they did before the mediocre Grin album is excellent. Their work with unorthodox song structures is similar to later Death. It's too bad the vocals suck.