Original Post
would this work out as a custom build?
External Hard Drive: ADATA - DashDrive DurableHD650 1 TB

Keyboard: Corsair - K55 RGB Wired Gaming Keyboard

Monitor (x2): Sceptre - E205W-1600 20.0” 1600x900 60 Hz Monitor

Case Fan (x3): Raidmax - NV-R120TP 64 CFM 120mm fan

OS: Microsoft - Windows 10 Home [64-bit]

Power Supply: BE QUIET! 300W Bronze Certified ATX Power Supply

Case: Cougar Challenger-B [black]

Graphics Card: MSI - Radeon RX 570 8 GB ARMOR OC

SSD: Western Digital - Caviar Blue 1 TB 3.5” 7200RPM

HDD (x2): Corsair Vengence LPX 8 GB DDR4-2400

Motherboard: MSI - B350 PC MATE ATX AM4

CPU: AMD - Ryzen 5 1600 3.2 GHz 6 Core Processor
I'll have more of a look at it, later, but one thing that stands out to me is the power supply. Your pc might not even start with a 300 watt power supply, and even if it does the power supply will be very inefficient at that capacity and won't last for long. Power supplies are most efficient at around 50% capacity, so try putting your build together on pcpartpicker, and then seeing how much power it requires. You will then want to try getting a power supply that has double the wattage your computer uses. Also make sure you get a good quality power supply; it is a very important component and will quite possibly take other parts of the system with it if it dies. Seasonic is a good brand, and most of their focus series of power supplies has 7-10 years warranty. Corsair also has some good power supplies, but don't get anything from the CX series.

If you tell me your budget, the country you are in and what games you will play on this computer, I can put something together for you on pcpartpicker. However, it might be worth waiting until next year if you can, as you have missed the Black Friday deals, and there will be new ryzen CPUs and AMD graphics cards in spring/summer.
You switched the names for your RAM and hard drive and you don't have an SSD so that would be a recommended addition.
I'd up the PSU to a 450 Corsair CX450M (it's not the old builder CX, these new ones are fine) and add a 240GB SSD from crucial or samsung which are rather cheap right now.
Also extra case fans aren't really necessary
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I looked at the new CX power supplies, and it does seem like they are a lot more reliable if they have a five year warranty instead of the previous 3 year warranty. However, I think 450w is still too low. 550w would provide more room for upgrades, and probably better efficiency as well. It also might be worth getting a TX power supply instead, as they are not much more expensive, but they have gold efficiency and a 7-year warranty.
Last edited by HAWK152; Dec 26, 2018 at 04:11 AM.
At this wattage I doubt it's worth investing in gold efficiency as you won't really see any difference anyways asides from warranty, which, let's be real, most likely isn't going to be used for 7 years.

That said the PSU that you chose is definitely garbage. First of all I don't really get the whole "silent PSU" thing, cause decent PSU should make 0 noise under optimal conditions. It's also non-modular, which will be pain in the ass to cable manage considering the size of your case. I'd suggest something from Corsair, semi-modular ones are quite cheap and reliable.

As Finn mentioned, get an SSD at least for your Windows installation. HDDs are slow, make a lot of noise and are generally quite unreliable in comparison to SSDs.

I don't really know much about AMD processors so can't comment on your CPU and GPU setup, though it looks quite balanced.

ADATA external drives are known to have weak connector points so it probably won't last you beyond warranty period, you might wanna keep that in mind.
The power supply may or may not be used for 7 years, but the warranty and efficiency is still a good indicator of the quality of the power supply.

Also, I don't see why this person might not be using their power supply in 7 years time. Computer parts are getting more power efficient, rather than less, and a 550 watt power supply today will still be fine in 7 years unless there is a major change in the type of connections used, and, considering we still have VGA connections on monitors, graphics cards and motherboards, I don't think a current power supply will be completely obsolete in only seven years.

Processor and graphics card combination is decent, but I don't think there is much point in buying computer parts now when CES 2019 is so close, and AMD is likely to announce new CPUs and GPUs that might either give you better value for money, or drive down the prices of current parts.