What memory to buy for macbook pro 17" early 2011? What brand/model of memory do I need to buy for a macbook pro 17" early 2011 model?  On Apple's memory page, they just say DDR3 1333mhz SODIMM.  So I went to purchase some from Newegg and happened to notice in the comments people complaining the mushkin RAM was not working on their macbook pro...

I just want to find the lowest priced working 8gbytes RAM.

Also, I assume Apple put 2x2gbytes in and I need to purchase 2x4gbytes to replace it.  Is it possible they put 1x4gbytes and so I only need to buy 1x4gbytes to add to it?
As long as the technical specifications (DDR speed, clock, physical size) line up to what Apple lists for your model MBP, you should be fine.

To answer your second question, that isn't possible. MBPs (along with every laptop I have ever opened up) contain only two RAM slots.