Buying new monitor, is dual monitor still good if different resolutions? And will it slow down PC?

[Luikkari]

Hello

I'm going to buy a new monitor for christmas. My budget is probably around 200 euros so I've been checking some test results and reviews and I think I'll buy this one: http://www.jimms.fi/tuote/9H.LA9LB.DBE What do you think about this?
I currently have a 60Hz monitor with a resolution of 1440x900. My question is will I be able to use my old one as my second monitor even though they're different resolutions? And would you even recommend it? And will it slow down my PC somehow? I play games alot so that's why I'm worried. Any kind of help is much appreciated. In case you would like to see my PC specs I'll put them below.

Spoiler

Asus GTX650-E-1GD5 NVIDIA GeForce GTX650
Western Digital Caviar Blue 500GB SATA3
Asus DRW-24B5ST/BLK/G/AS 24x DVD+/-RW
AMD FX-4100 3.6 Ghz 4-core Black Editon
Asus M5A78L LE 760G AM3+ ATX emolevy
Kingston Valueram 4 GB 1333 MHz DDR3
Codegen midtowerer
550w PSU

 

[Barney6262]

That monitor is a good monitor, BenQ are a reliable manufacturer so you should not have any issues with it.

Typically, Dual monitor setups are not very useful. Unless you plan on using the second monitor as one to control music or something. Having the two side by side displaying the same screen is a terrible idea as you will not only get a stark difference in size/res you will also get the Bezel in the middle of the screen.
Running two screens will slow your computer down, it is rendering even more pixels.