New monitor, Dual screen setup, 4850.... a couple of small questions

So i am looking into buying Samsung T240HD(1920*1200) to replace/work-with my Samsung 932BW(1400*900)... (i need the tv tuner and speakers on it since i live in a dorm and i am planning to use it as my TV also)... now a few questions...
Last time i checked you can't run 2 monitors at the same time with different resolutions... is that still the same?
I game quite a bit (L4D2, TF2, CSS, BF series... everything from old to the very new) i am quite use to all settings maxed out on at 19", but i know i will have to tone that down a bit which is perfectly fine... the question is how much of a stress will an extra monitor on the side, open to desktop with nothing intense going on, cause on my 4850... in other words, is the processing power split 50/50 between monitors.... or more like 95/5?
Last thing, from personal view, how bad do you think 1440*900 resolution looks like on a 24 inch?

ty  

EDIT: and another question... how do you think 4850 fairs in 1920*1200? i know the fps... i am just asking what settings is the game smooth under from personal experience: Low, Medium, or High (obviously i very much doubt high)?