upgrading from a mainly a visual aspect.

I have a older MBP. Its a 2.0GHz core duo(pre core 2 duo) and has already been upgraded to its max of 2gb ram. I do a lot of photo editing on a separate Dell monitor while I watch tv and movies on the 15" monitor. Now Im wondering if I should pick up a better external monitor(looking at a 20" cinema display for $300) or if I should save that money and put it towards a 2.4 or 2.66GHz 20" aluminum iMac? If I did that then I could also eventually move to 4gb ram which I cant do on my current MBP.

So basically in lame man's terms. Will upgrading to a aluminum Imac make my pictures and movies appear more appealing then they would be on my older MBP and a 20" cinema display?

 

I take it to class with me but I wouldnt be getting rid of it if I got a imac. I just wouldnt be getting the cinema display.

 

I was thinking the same but now I am being told I could get basically the same monitor from a different company for cheaper Im obviously inexperienced with this stuff but I really dont want to spend un needed money on a monitor thats no better then a cheaper one.