I will back up anyone who says buy Bob's book. Bob is a one-of-a-kind guy, and has a heart for teaching. If you notice in the thank you's in the front of the book, he thanks all those that will come after him, so he's not just another "Mastering Guy". I have a chance to meet Bob and go up to his studio next month, and I can't wait.
So to your question of monitors... how about your converters, Lavry makes a great set for about $8,000 and then you may want to buy a Sadie system, and maybe the GML Mastering series EQ (around $8,000), but I'm with Blue Bear when he recommends the Adam monitors, although Dynaudio does make a set for about $19,500! And have you thought about 5.1, just multiply the costs by 10.
So to anyone who craps on Blue Bear for trying to let this guy know that you CAN NOT just grab some mid level gear and start mastering, why are you here. You're not helping anyone by telling them that they can do it.
Just my .02
Later,
musik