upgrading RAM in 2010 i7 model finding less expensive ram

[Sossity]

I got the stock 4gb, would I feel much of a difference with 8gb?

will it void my warranty?

& is there good compatible RAM for this under $100.00? or under $150.00? I am looking for the chapest possible but dont want it to be incompatible either.

or would getting an external monitor be better?

would upgrading RAM be more effective than a SS or solid state drive?

I am using Adobe CS5 software, indesign & photoshop.

 

[toxic]

8 GB is probably worth it for you. any DDR3 1333 SO-DIMM will work.

 

[Sossity]

8 GB is probably worth it for you. any DDR3 1333 SO-DIMM will work.

could you link me to the least expensive memory? thanks