What CPU would be the best bang for your buck on a 400$ gaming PC?

I want to know what CPU is the best bang for my buck for my gaming PC build
in 2017. I want to see what processor would give the best performance and I'm planning to use a Sapphire RX 460 NITRO. I chose a AMD Athlon X4 845 but if there's a better option out there please let me know.

Airplane button is not working in my Lenovo u41-70?

I have no problems in switching the airplane modes manually by clicking it on the screen but when I try it to toggle the airplane mode on and off through keyboard, there's no response… It seems as if I have pressed nothing.

Pc not accessing full amount of ram?

My pc is 64 bit os with windows 7 home premium and I installed 2x2gb of ram but it says there's only 3gb of ram. I understand that 32 bit os can't access the full 4gb but mine is 64 bit and I've restarted 3 times

Lenovo m58e memory upgrade?

*ENGLISH NOT THE FIRST LANGUAGE* so i have 4 gb of DDR3 memory, but i want 8 gb of memory. So can i change it to the 8 gb of DDR3 memory

Play Store not working on Lenovo K3 Note?

I bought it off of Gearbest. Turns out they put their ROM on top of Lenovo's.
When I was prompted to update the software, I accepted, not knowing it plans to topple Gearbest's ROM. It appears it didn't do it well, and ****** up the compatibility, so I keep getting "Google Play stopped working".
I snooped around the internet for a solution (delete data, cache, restore to factory settings etc), and none of which worked. I even tried to uninstall all Play updates, but the phone uninstalled Play as a whole.
I reinstalled via multiple apks, and none of which allowed me to open Play Store. It would crash upon opening. Heard if I flash a new ROM, it'd be fine. Tried that. Couldn't flash it "because phone wasn't rooted". So I tried to root it. Nope.
Tried to download a workaround, to avoid Play Store. Couldn't install any of them either… Help.

Upgraded old dual core cpu with quad core cup and now the pic won't boot up?

The motherboard and the new cup both have the lga775 socket so I don't understand what the problem is. The "new" cpu is an Intel core 2 extreme qx6700. Can anyone help me understand what the issue could be? Because clearly the socket isn't an issue and I thought that was pretty much the determining factor. Sorry for making anyone think hard since its older hardware. I don't have the budget for anything new right now so I'm trying to make do. The pc is a Lenovo ideacenter k300.

What's wrong with my computer?

I'm on a Windows 7 Lenovo, and my computer keeps bugging out. What happens is it scrolls down and to the right rapidly, acting like I'm holding those keys down. This goes off and on every five minutes or so. I've restarted my computer multiple times, and that did nothing. Virus scans showed up nothing. What can I do?

What kind of Graphics Card can I use in my LENOVO H50 - 90B700ENUS?

What kind of Graphics Card can I use in my LENOVO H50 - 90B700ENUS? - 1

Added (1). LenovoModel
H50-50 (90B700ENUS)
Intel Core i3-4170 3.7 GHz
64 bit Dual Core Processor
4 GB DDR3 1600
500 GB 7200 RPM
Intel HD Graphics 4400
Power Supply180W
Windows 10 Home 64-Bit
Motherboard Chipset Intel H81
Intel Core i3 4th Gen
CPU Speed
4170 (3.70 GHz)
L3 Cache Per CPU
3 MB
CPU Main Features
64 bit Dual Core Processor
GPU/VGA Type
Intel HD Graphics 4600
4 GB DDR3
Memory SpeedDDR3 1600
Memory Slot (Total)2
Maximum Memory Supported
16 GB
PCI Slots
1 PCIe2.0 X16
3 PCIe2.0 X1
1 Mini PCIe2.0