Monitor Causing Performance Drop?

Hey guys, I posted about a week ago about a good monitor to buy to replace my 15" LCD acer AL1511. I ended up buying the 24" ASUS VW246H

The problem I have is with performance. My computer can run every game I have very smooth at max graphics settings including the latest Empire:Total War, so I don't believe hardware is the issue.

My problem is that when I hooked up my ASUS monitor, I noticed a significant performance decrease. Mostly noticeable on ETW but a little bit on other games as well such as Company of Heroes and even Medieval 2: Total War.

The new monitor is better than my old one in every way so would there be a reason why, when I hook up my new monitor, I get a large decrease in performance?

Also, does anyone know of a good way to "calibrate" a monitor to get the best display? Ive been toying with it but I must be really bad at it...

Thanks in advance!

Tommy

well I actually only really use the computer for gaming so I was looking for a computer with respectable resolution (anything higher than 1024x768) that wouldn't cause such a performance decrease. My video card is a 9800GT so I don't really wanna get a new one. You're advice was very helpful, do you think if I get, say a 19 or 20 inch monitor instead, at a lower native resolution, that the performance would change significantly? I'm not really sure how else to test this.

Thanks!

well I actually only really use the computer for gaming so I was looking for a computer with respectable resolution (anything higher than 1024x768) that wouldn't cause such a performance decrease. My video card is a 9800GT so I don't really wanna get a new one. You're advice was very helpful, do you think if I get, say a 19 or 20 inch monitor instead, at a lower native resolution, that the performance would change significantly? I'm not really sure how else to test this.

Thanks!