Help with pc build. What would improve it?

So i need someone who is very educated and can suggest extra parts to improve my pc's general performance, boot time, load times, faster rendering times for videos and ofc fps on games...
Currently i have:

This pc is not custom built and is manufactured by ZOOSTORM
CPU: i7 4790 (non k) not overclocked and cant be overclocked, its running at 3.60GHz
GPU: GTX 970 EVGA SC
RAM: 16GB of DDR3 1600 MHz
MOTHERBOARD: Gigabyte B85-HD3
HDD: 3TB Western Digital Green (no ssd and i get 100% disk usage so i think i need a new one) :/
PSU: CX750M (Coil Whines when playing games)
I need to get something to speed up my boot time as it takes about a minute to load and load times are very long. Fps gets quite low at ultra 1080p from time to time. I want to SLI my gtx 970, so i need to get a motherboard that supports it. Any idea on what motherboard or if sli is a good idea. Also is it worth getting an SSD or new HDD? Another thing i keep thinking of doing is getting the k version of my cpu but do you think its worth that much just to have over clocking capability?
I would really appreciate help on what to do as my pc needs upgrading. Load times are awful fps on games like fallout 4 and others have spikes to 40fps when around alot of objects

BunnyJ said:

The system looks good I would just use an SSD for OS/Programs. That's the best improvement you can make. And I wouldn't bother with a different motherboard. It's not going to effect performance, IMO.

Just get an SSD.. 200Gb or more.

Jeff

Is it the gpu that loads in all the objects in games? I tend to get lag in the vertibird on fallout 4 as I can see so many objects ( get about 40fps)

What screen do you have?

Joshy said:

What screen do you have?

if by screen you mean monitor i have a aoc E2770S, Why?

BunnyJ said:

What you can do is get a better graphic card and that would help that out a lot.

ahh not sure if its worth it tho. Only bought this gtx 970 2-3 months ago. Would a gtx 980 be really that special?

BunnyJ said:

Just a thought.. I think the PC you have is nice and adding an SSD would be the best improvement you can do to it.

Do you think a new HDD will sort out the disk usage? My disk usage is awful

Ludicrous said:

if by screen you mean monitor i have a aoc E2770S, Why?

Because you failed to report what resolution you play So you have a 1080P/60Hz monitor and you think a GTX 970 cant handle it?