I have the i7 model and it's served me well the last 4 years. Use it for photoshop, illustrator, premiere pro, etc and generally it runs well, but if i keep them open for too long (sometimes days, sometimes hours) then everything starts to lag.
That's why i'm considering an SSD upgrade. Thinking Samsung but honestly i don't know much about SSD's so, what would you recommend? I was hoping not to spend more than $150 as i also have to replace the battery. Also, do the 16gbs of RAM really make much of a difference?