Buying new iMac in the next 6-8 months

It is possible, via Thunderbolt or Firewire 800 (via Thunderbolt <> Firewire 800 adapter) or USB 3.0.
The USB 3.0 option would be the cheapest and simplest, good enclosures for 3.5" HDDs can be had for around 30 to 40 €, Firewire 800 enclosures are a bit more expensive (70 € + 30 € for the adapter) and Thunderbolt enclosures are quite expensive, plus the TB cable costs another 50 €.

USB 3.0 is more than fast enough to saturate the HDD's read & write speeds.

appstate said:

Thanks simsaladimbamba!

I thought the mid 2011 mac is not USB 3.0 compatible? Since I'll be using it for a second display, I was hoping to also use the HDD as a second drive.

Click to expand...

But the iMac from 2012 and the possible iMac you buy (2013 or 2014 model) have USB 3.0, thus you could connect the HDD to that iMac via USB 3.0, but if you want to run the old iMac as second display, it needs some OS to boot from anyway, thus you could just let the HDD inside the iMac and leave it as it is and use it via network or if TB allows that, via that.

You could however do a CLEAN INSTALL of whatever OS you want on the old iMac on a smaller partition of the HDD (let's say 25 GB or so) and use the rest as data drive, no need for convoluted folders and such.