I have the 15" MBP Unibody computer in my sig. I have the 2gb of RAM in it. Opening up programs seems to take forever and it just seems sluggish. I know a ram upgrade would help and it's cheaper than a SSD, but what about these options: 4GB Ram vs 128 GB SSD. I mean, I could go for both, but probably won't. Which will increase my performance more?