Nothing there is going to be very demanding for the processor, graphics card or RAM.
Essentially, the laptop only needs to output one data stream.
Any of the i3/i5 dual core CPUs, any modest graphics card like a Geforce 310M or i3/i5 Sandy Bridge integrated HD 3000 graphics, plus 2GB or more RAM will get the job done.
Upstream from the laptop:
(1) You'll need a video splitter something like this IOGEAR 4-Port HD Audio/Video Splitter
The bigger challenge is going to be getting cables to hook up the splitter output to the four external devices without exceeding the max distance for the type of cables in use. Which might drive the need for a more advanced splitter box and amplifiers for long cable runs. You'll have to look at that cost vs a wireless setup, depending on how you have the displays situated.
(2) If your projector/TVs are 'network ready' you can go with a router/wireless router which will probably be more flexible than the simple video splitter.