Well since you can't play online games with an xbox and you can with a PC you should probably factor in +$240 for 4 years of Xbox live then.
And I fail to see how $50 xbone pad and Bluetooth is mandatory for a PC. If you're going to say that you get into kbm adapter territory for the Xbox and unnecessarily buying a kbm just for the Xbox.
Either way both systems come out to $700+ if you don't want to extremely limit your budget on the PC build and we include 4 years of Xbox live as you cannot play online multiplayer without it. $500 if you really limit your PC build and $500 if you don't play Xbox games online.
1. The whole point is to build a console replacement targeting 4K/30fps. This should include: Win10, mini-itx case, quality PSU, mobo, CPU, GPU, RAM, HDD, optical drive, quality KB/M or cheap KB/M and nice gamepad, and hdmi cable.
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2. You're fluffing your build cost by: 1. Excluding Windows 2. Excluding KB/M 3. Excluding gamepad 4. $15 firehazard PSU 5. Excluding optical drive 6. Big honker ATX case 7. No HDMI cable
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3. A baseline build estimate looks like: $40 Case, $30 PSU, $50 Mobo, $45 RAM, $45 HDD, $45 BD drive, $20 KB/M, $50 gamepad+receiver, $90 Win10, $5 hdmi.
TOTAL = $420
That leaves CPU and GPU budget of $80 for a $500 build, or $180 for a $600 build. We know GTX 1060/RX 580 run ~$250 and an i3 starts around $120. That's
at least $350 even with $20 MiR.
Putting us at:
$770 for i3+GTX 1060 or RX 580
$840 for i5+GTX 1060 or RX 580
$920 for i3+GTX 1070
$990 for i5+GTX 1070
This is mini-itx. The best deal on big honker ATX case build is ASUS prebuilt for $950 with i5/GTX 1070. Let's just be honest that right now, it's about $900 to beat the X1X without accounting for UHD Blu-Ray.
Do a build list on pcpartpicker or newegg with all the requisite components and post it here I'm curious to see what you end up with.