I7 Laptop Buying Advice

I am looking to buy a new laptop in a few days. Budget of around $1500

I plan on doing some video editing/audio editing as well as lots of Photoshop use and other graphics editing. Maybe I will do some gaming but I mainly game on my xbox... also would like to be able to watch HD movies on my laptop..

anyhow I am looking at the Sony F Series i7 laptops... they seems to be getting good reviews... here is one things i am a little unsure of... there are 2 options (and i see alot of laptops havin these 2 kinds of options)... one for full 1080p and then there are others with 900p or 780p resolution on the laptop screens. Here is the thing, i am going to be hooking this up to my 27" HD Monitor via hdmi (or RGB depending on which is better).... if I get a laptop that does have a nice ATI or nVidia gfx card, can i output my laptop via HDMI to my new monitor in full 1080p even if the laptop screen resolution is only 900p? If someone could shed some light on this subject for me, that would be great. I could use to save a few $$ if the laptop screen doesnt do full 1080p just as long as the hdmi output will do 1080p... again i am looking at the F series by Viao ...

also, do you think 4gb is enought ram, or should i throw down the extra $ for 6 or 8 gb?

Thanks guys!