Yeah... I'm way behind on both bands actually. After a long time not standing Mustaine's voice, I finally seem to appreciate it along with the excellent music he creates, so I'm following the Walnut's guide to Megadeth. Even though I didn't get Killing is my business.. first. So now I have Peace Sells, Rust in Peace aaand uhm, Cryptic Writings.
I am also way behind on Atheist. Remember hearing them once, and figured out that I should look into them. So I finally did, after I found it rather cheap on eBay.