the graphics card is VERY important ! that is where the speed comes from. Altium uses directX HEAVILY. they have a list of tested graphics cards.
1920x1200 (not 1080 but 1200 vertical. you can never have enough real estate)
I travel a lot & work out of several offices. I use a 4 year old Toshiba Satellite Pro L500 laptop - Windows 7 Pro 32 bit with 4GB (only 3GB is accessible) Intel i5 M520 @ 2.4GHz. Video card is an ATI Mobility Radeon HD4650 with 1024MB of dedicated memory.
I plug in a keyboard & monitor (LG W2442PA 1920 x 1200dpi ) at each location.
Works fine, very stable. You will just likely need a bit more processing power when laying out full panels or when having a half dozen pcbs of reasonable size open at the same time.
Just as the video card is very important, so too is using an Intel processor as Altium ONLY test using Intel. There is a recent thread on eevBlog where users are complaining about Altium crashing. I can't say I remember the last time Altium crashed on me & I do wonder how many of these others users are not running an Intel main processor or a reasonable video card.