I am planning a new build of a DAW PC. I have ordered a couple of key parts already. I will be reusing a few of the existing components from my current system.

CPU: i7-6850k
Already ordered.

Motherboard: MSI Gaming Pro Carbon
Already ordered. Ex-demo.

Case: Fractal Design Define R5
I haven't ordered it yet but I'm pretty much decided, unless anyone has any better suggestions.
UPDATE: Fractal Design Define R5 case now ordered.

RAM: 16GB 2400MHz 4x4GB
There are plenty of options for 2400MHz 4x4GB, but I will probably go with
Corsair Vengeance LPX 16GB (4x4GB), PC4-19200 (2400MHz) DDR4, 14-16-16-31
I don't even really need 16GB. My current system only has 6GB and never maxes out.

Drives: Multiple
I'll be adding a new 240GB SSD for the operating system (Windows 7), but others will be transfered from the old PC. Probably 6 in total (including 3 SSDs).

GPU: Matrox M9148 (existing)

PSU: Undecided

Cooler: Undecided
Needs to be quiet.

Comments welcome, especially on PSU and cooler.

By The way, until recently, I wasn't really intending to replace my current system yet, as it still runs ok. However the family computer is over 10 years old and has been developing problems lately and needs to be replaced before it fails totally. The plan is, after getting the new DAW PC up and running, to use the previous DAW PC (or what's left of it) for the family.

Hi Kev,
Just bumping up this thread....
 
Regarding coolers, I have the NH-D14 which is very quiet, but it's huge. It should fit in a full ATX case (I believe your Fractal case is an ATX). The NH keeps things very cool (around 35 degrees). Another recommendation (from Fireberd/Jack) is Deepcool Captain 240EX and it's a water cooler (full kit).....if you're inclined to go that route. 
 
The EVGA SuperNOVA G2 850 80+ Gold has got good reviews, but it maybe a bit more wattage than you need....IDK?
Fully modular PSU should make things super easy with cable mgt./installation.
 
Best of luck mate with your upgrade and having extra RAM is always a good thing (even if you don't use it).... 
 
        

I would go for 2 x 8GB ram rather than 4 x 4GB to leave room for future expansion (assuming the MB has 4 slots).  There shouldn't be much difference in price.
 
AMB
 

Mesh
Regarding coolers, I have the NH-D14 which is very quiet, but it's huge. It should fit in a full ATX case (I believe your Fractal case is an ATX). The NH keeps things very cool (around 35 degrees)...

 
I was considering that one until I watched a video about installing it. It's so huge in size that it gets in the way of other components. I'm not ruling out liquid coolers.

AntManB
I would go for 2 x 8GB ram rather than 4 x 4GB to leave room for future expansion (assuming the MB has 4 slots).  There shouldn't be much difference in price.

 
I'd been led to believe that using 4 slots rather than 2 allows more bandwidth. Is that not true?

AntManB
I would go for 2 x 8GB ram ... to leave room for future expansion (assuming the MB has 4 slots).

 
I probably won't need more. My current system only has 6GB and never maxes out. When I built it I had the intention of adding a further 6GB later, but the need never arose. I don't have Kontakt or anything similar that requires large amounts of RAM.
 
The new motherboard has 8 slots.

Mesh
...Another recommendation (from Fireberd/Jack) is Deepcool Captain 240EX and it's a water cooler (full kit).....if you're inclined to go that route. 
 
The EVGA SuperNOVA G2 850 80+ Gold has got good reviews, but it maybe a bit more wattage than you need....IDK?

 
Thanks. I'll check these out.
 
I won't order the cooler yet until I've got the case and examined it in detail. Last time, I initially purchased a water cooler (I forget which model) and could not get it to fit properly with the case layout and ended up returning it. The problem was really due to the tubes not being sufficiently flexible for the required configuration.
 
Still not sure how much wattage I will need yet.

One problem that I have with the PSUs that I've seen is that they all seem to include so many outlets that would be unused in my system. For example, those PSUs in the EVGA range all have 4 separate GPU outlets. My graphics card doesn't even need to connect to the PSU. They all have a 2nd CPU outlet too. That a lot of waste in total.

A "fully modular" power supply is the way to go.  Extra, unused, connections do nothing.  They don't get in the way or cause any power supply problems.  
 
Two or four memory modules, from what I've found, make no difference in bandwidth.  However, you need at least two (of the exact same brand/type) for proper dual channel operation.