Thinking about getting a macbook pro and using it with an external monitor. This will be my "desktop" and probably won't move much. So, I was wondering, with the external monitor connected and when I power on will the external automatically come on? or do I have to manually turn it on every time I boot up? Really wanted to buy the 24" iMac but the thing is sooo much taller than my current 24" monitor that it just wouldn't work. Thinking about the 20" + 24" external also. Thanks.