Which to Upgrade first? My Amplifier or Speakers?

I have owned a nice system for years, but I am hardly an audiophile. You people impress me with your depth of knowledge of audio. I've been following this site for some time. This is my first post.
From time to time I replace or upgrade components. I've got a tricked out Linn Sondek LP 12 turntable. I recently acquired a McIntosh MP 100 phono amp and am hearing LP's now that exceed anything I've heard on CD's and equal if not exceed the output of my SACD's. I bring this up only to give a flavor of what I listen to.
The issue is as follows: I have a McIntosh MC 206 Amp that I bought in 2003 that puts out 200 watts per channel. I have no issues with it, although I've never had anything to compare it with. I've read some impressive reviews of how much of a difference an amplifier can make to the quality of sound output. For speakers I have Magnepan 3.6R's that I also bought in 2003. I love them. I can only afford to upgrade one at a time - let's say in the neighborhood of 10 - 12K. So, I'd like to hear what this august body has to say about which I should upgrade first and why? The amp or the speakers? Thank you.