How to get the right information for iMac upgrades

you have a mid 2011,

There are a lot of upgrades possible depending on what you want.

The cpu can be upgraded, but you already have the i7 model, so that's not interesting.

The videocard can also be upgraded to a model with more videomemory, but that is pretty expensive and these videocards often have issues.

The ram can be upgraded: iMac Intel 27" EMC 2429 RAM Replacement

you can upgrade the harddrive to an SSD. which is possible in three different ways:

1. replace the HDD with an SSD

2. replace the disc-drive with an SSD

3. put an SSD behind the disc-drive.

to upgrade to an SSD you need the right cables and brackets and you use a regular 2,5" sata SSD.

This guide explains how to do option 3.

Installing iMac Intel 27" EMC 2429 Dual Drive Kit (HDD or SSD)