Upgrade Question

Even a 2011 'Sandy Bridge' iMac like mine would be a big improvement over the core 2 duo, how much that actually translates into real-world speed improvements depends on what programs you use and how you use them.

Hard to say without actually knowing you're specific day to day usage, simple things like, 'do you leave tabs open while browsing or close them all down?' play a huge part in how much RAM you should get. A general recommendation would be to stick with standard 8GB which would satisfy most average users' needs, if after using it for a while you find yourself needing more then chuck in some more.

(Of course if you're going for the 21.5" iMac you won't be able to upgrade the RAM later, so it's up to you if you want to upgrade at the time of purchase for peace of mind or maybe test out an iMac somewhere first?)

An i7 is basically an i5 with the addition of hyper-threading (virtual cores), from what you mentioned I highly doubt you would ever use this feature, save yourself the money and spend it on more RAM or Fusion/SSD.

If you're looking for responsiveness this is what will do it. In a Fusion arrangement all of your most frequently used items will be moved to the SSD portion. This means applications and files will open and be ready to use a lot faster than a traditional HDD. Basically all those moments you spend simply waiting watching items bouncing in your dock will be cut down to a second or two. Traditional HDDs also have to spin up to speed if they've gone to sleep, you will see this as your Mac temporarily freezing with the spinning beach ball when you try to open a video for example.

No Problem, just remember not to take my word (or anyone else' for that matter) as gospel. Multiple opinions from multiple sources make for the best decision.

Good luck with your purchase!

 

An SSD is probably one of the most-impressive performance upgrades you can do. I am now exclusively SSD on all my machines.

 

If you get the 21.5" go for 16GB of memory -as this need to be configured at the time of purchase. If you get the 27" start with 8GB and if it turns out not to be enough, buy a 8GB or 16GB memory kit to add to the 8GB already in the system. I'd recommend Crucial as one of the choices for RAM.

From your usage, go with a Fusion Drive - 1TB or 3TB as needed.

Unless you are doing heavy video processing, the i5 will be more than enough.

 

I'd probably consider putting an SSD in your older Mac if it's still good enough for most of your needs. As has been said though, the difference between Core 2 and Core i series chips is quite extensive, and yes, I've used both (in MBPs).