I'm looking to buy a Mac Mini to replace my windows PC, but I don't know which one I should be aiming to get..
The 2.6Ghz Quad with 16GB RAM and a Fusion drive will cover everything you want to do. Just by coincidence, it will also cost you the most.
But I warn you, you will now get a whole bunch of forum members who do not own the 2.6Ghz telling you you don't need it Don't listen to them It is sort of like someone driving a Toyota Prius telling you you do not need a Ferrari to get from A-Z. True, but hey... it is a lot more fun in a Ferrari and you get there so much quicker!
You can save a few dollars with getting your own RAM. I use two 8GB Corsair Vengeance chips (16GB total). It is very easy to install.
If you are adventurous you can also do your own hard drive install such as an SSD (instead of getting it from Apple). But if you are use to doing that on PCs, it is nothing like the install on a mini.
See the OWC website or iFixit if you want to see if that is your cup of tea.
My recommendation is to go with the quad core as well. I think for memory 8 or 16gb will be fine. I'm not sure how memory intensive video editing is so I'll defer on the memory requirements but its better to have too much ram then too little.