Issues extending Retina's desktop to 1080p (1920 x 1080) monitor?

Am looking to buy a retina MBP and want to extend my desktop to a 1080p (aka 1920x1080) monitor. Have looked around extensively, but am totally confused if I'll run into issues with this. Am currently running a similar setup now with my 2009 17" MBP and an external 1280x1024 monitor and it's horrible. External doesn't show all the desktop it should, the hidden parts of that desktop are inaccessible, etc. Will my proposed new setup have these issues? Can I get both to run at 1920x1080?

Thanks ahead of time for any help!