I have a 1st gen Core 2 Duo 17" Macbook Pro and it has 2gb Ram, Will i notice the difference if i put in 3gb RAM?
If you're using PS a lot (which you are!), then definitely go for it!well a 2gb stick can be as cheap as £65 now so not too band. I am self emplyed web developer so Photoshop, Dreamweaver and the spinning beach ball are always open.
In theory, that should be the case, but the OWC benchmarks for MBs with multiple memory configurations show that there is a performance advantage having more memory (whether or not the sticks are matched) and user reports (e.g. on this forum) have the same conculsion.If you need more than 2GB you will (atleast if it's already single channel.)
If you don't you won't, or it will become slower (due to single channel and therefor half memory bandwidth.)