2011 Air, where next?

[rare]

Okay, so I sold my desktop as I rarely got to use it these days. I use my air all the time, mainly for doing uni work. But since I sold my PC I am using my air all the time as my main machine. It works absolutely fine most of the time (i7, 4GB, 256SSD) but I do get some slow down when trying to do heavy multitasking, and the 13 inch screen isn't really big enough for working at home.

I was looking at a retina pro but I am concerned about all the screen problems and sluggishness I have read about. I was thinking perhaps get a previous model 15 inch Pro, with a ram and SSD upgrade? I would assume a higher end last years model (perhaps?) would still be much quicker than my Air, while offering a larger screen and still having the ability to move it with me wherever I go. Also, there seem to be quite a lot for sale on auction sites etc, so could save a small fortune over buying a brand new 2013 model.

Thought any one, as I don't know much about the previous generation Pro's and whether or not they would be much of an upgrade as my Air was a pretty high spec when I bought it.

 

[rare]

Trouble is the Air ram is non upgradable, as far as I am aware. Do the 2013 airs come with more ram now? I will have to check it out.

 

[rare]

I am sure it is the 4GB causing the problem. I multitask as in plenty of PDF's open, lots of word documents, many many windows in safari, itunes, that kind of thing. I would really like a 15inch screen, but I simply don't think I can justify the cost of a 15 inch retina, so I am still considering the previous generation pro with lots of ram and a large ssd. Especially the cost which apple charge for ssd's which is ludicrous.