One of the clips probably didn't slip in all the way the first time so the cooler didn't get proper contact, but enough for cooling idle/throttled. I'm speaking from experience.

I don't know a single CPU that throttles at 70°C.

You know that you can't just reseat a CPU cooler without replacing the thermal paste (most of the time, there are exceptions)?

No, CPUs don't explode, only bad PSUs do that. Iirc Sandy Bridge throttling starts at 93° and ends at 98° (Tj max) where the throttling becomes ridiculous, past that -> shutdown. No explosions

Yes, the throttling is evident in the task manager screenshot.
Have you reseated the cooler or accidentally loosened one or more screws/plastic clips?

Check temps.

#23

#24
I can deal with people saying CPUID instead of CPU-Z, but if you mean hwmonitor say so. Otherwise it's just a guessing game. CPUID is not a program, this is the equivalent of recommending "Microsoft" as an OS.

#684
In that case forget the bundle. A refurbished Z87 Extreme 4 is cheaper. 390 because it was still within budget.
http://pcpartpicker.com/p/8vpwsY
Or a µATX Skylake build because probably won't go Crossfire/SLI anyway so there's no need for full ATX.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-6600K 3.5GHz Quad-Core Processor ($219.99)
CPU Cooler: CRYORIG H7 49.0 CFM CPU Cooler ($34.50 @ Newegg)
Motherboard: ASRock Z170M Pro4S Micro ATX LGA1151 Motherboard ($98.99 @ SuperBiiz)
Memory: G.Skill NT Series 8GB (2 x 4GB) DDR4-2400 Memory ($49.99 @ Newegg)
Storage: Samsung 850 EVO-Series 250GB 2.5" Solid State Drive ($84.89 @ OutletPC)
Video Card: PowerColor Radeon R9 390 8GB PCS+ Video Card ($299.99 @ Newegg)
Case: Cooler Master N200 MicroATX Mid Tower Case ($43.99 @ SuperBiiz)
Power Supply: Cooler Master VSM 550W 80+ Gold Certified Semi-Modular ATX Power Supply ($49.99 @ Newegg)
Monitor: LG 23MP47HQ 60Hz 23.0" Monitor ($119.99 @ Newegg)
Total: $1002.32
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-10-16 09:25 EDT-0400

#685
Workstation? Did you mean office pc?
PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i3-4170 3.7GHz Dual-Core Processor ($114.99 @ NCIX US)
Motherboard: ASRock H97M PRO4 Micro ATX LGA1150 Motherboard ($62.98 @ Newegg)
Memory: Team Dark 8GB (2 x 4GB) DDR3-1600 Memory ($37.99 @ Newegg)
Storage: Samsung 850 EVO-Series 120GB 2.5" Solid State Drive ($63.89 @ OutletPC)
Storage: Seagate Barracuda 2TB 3.5" 7200RPM Internal Hard Drive ($63.00 @ Amazon)
Case: Fractal Design Core 1000 USB 3.0 MicroATX Mid Tower Case ($28.99 @ Newegg)
Power Supply: Corsair Builder 430W 80+ Bronze Certified ATX Power Supply ($19.99 @ Newegg)
Total: $391.83
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-10-16 10:35 EDT-0400

Skylake i3 and Pentium availability is still basically nonexistent sadly.

5.1/7.1? Are we talking about a preamp?

Check ipconfig again

-DNS to automatic
-test if it works
-disable ethernet and enable it again
-test again
-reinstall the drivers
-test again

So DHCP is enabled but ipconfig /all says it's disabled? Congrats, you broke windows.

You probably should have told us that. It's kind of important. You should definitely check your settings, especially IPv4.

Getting no connection at all on the pc though?

You might want to check your settings.

Which powerline adapters exactly?
Does ethernet directly still work? Are the adapters dead (there should be some indicator leds)?
Static IP or DHCP?

How old are the powerline adapters?
Got a second pc at hand for testing?

Turns out your replacement choices are correct, but everything is more expensive.
Except for the PSU. Get the CS450M instead. http://www.playtech.co.nz/afawcs0139235/CATID=1078/ID=22294/SID=177618113/productdetails.html

Keeping a new heatsink clean won't be any easier, so stick with cleaning it and applying new thermal paste maybe once every year, even every 3 years is fine.

Get some isopropyl alcohol, preferably 99%, less is fine but with e.g. 70% you'll have to wait a bit longer until it's dry since the water takes far more time to evaporate than the alcohol.
Some thermal paste, if you need it. <10$ and >3g, everything else is terribly overpriced. MX-4 and NT-H1 perform well.
Total <20$ and it should last you a long time. 3g are enough for at least 3 applications and the alcohol should last an eternity if that's all you use it for.