RAM Upgrade Path

[deadfolk]

Okay, so RAM is somehow something I've never gotten my head around, compatibility-wise! I would be grateful for any advice on the following.

I have 2x4GB DDR3 in my PC right now. If I want to go to 16GB total, what are the rules/recommendations/considerations?

1) Is it best to throw out the 8GB I have and replace with 2x8 or just add another 2x4?

2) If the latter, does it need to be the same as the existing stuff?

3) Do I need to worry about speed? I'm not overclocking right now, but possibly in the future. I'm running an i7-4770k.

4) Anything else I need to consider?

 

[deadfolk]

This fellow: Gigabyte Z87-D3HP Intel Z87 (Socket 1150) DDR3 ATX Motherboard
With this RAM: Avexir Core Blue Series 8GB (2x4GB) DDR3 PC3-12800C9 1600MHz Dual Channel Memory Kit (AVD3U16000904G-2CW) - Blue Light

 

[deadfolk]

http://www.overclockers.co.uk/showproduct.php?prodid=MY-078-AR&groupid=701&catid=8&subcat=1392

Still sell that RAM.

I'm confused - that's a 8GB kit. If I went with that I would need to keep the RAM I have.

To be honest I doubt I'd sell it anyway - too much hassle.

What about this stuff?
TeamGroup Vulcan GOLD 16GB (2x8GB) DDR3 PC3-12800C9 1600MHz Dual Channel Kit (TLYED316G1600HC9DC01)

It's 16GB for only ~£12 more than another 8GB of what I have.

Edit: Is that the stuff you were talking about?

 

[deadfolk]

Got it. Thanks everyone - I seem to have the info I need to make a decision now. Have a good weekend!