What CPU and what PSU for this GPU

So im getting asus r9 270 tomorrow and, since all the things in my PC are shit i now need to upgrade my CPU so it can keep up with the current  games. I was planing to get AMD FX 6350, your thoughts. Am I completley wrong with the CPU or is it OK. And how powerfull of a PSU do i need. I now have 400W PSU. Is that enough? 

I also have 3 HDD's 

For a PSU I'd look for something with at least 650W, just to be on the safe side, and to make it somewhat future-proof for any other components you might get later on. Not sure about CPU, never had an AMD CPU. I currently have an Intel 3770K with an AMD 7970 Ghz edition card and a 675W PSU, never had any issues.

The 6300 is from 2012, and is starting to age, concidering it's still $99+ everywhere. With how uncertain the amd upgrade path is, i'd reccomend waiting to see the 20th anniversary pentium with a decent cooler, which will OC, and have a better IHS. It should be great value, and you can spring for an OC-able cpu later. 

for the psu, I'd get a 450w+ concidering the 270 only has one six pin, and intel parts are <84w mostly. 

Don't get the 6350. Get the 6300. 

It is an absolutely fabulous CPU. It is fast and can be easily OCed and will offer plenty of power. It is a great value and will do better than the Pentiums even if they are OCed. 

500W would be plenty. The CX500 from Corair is decent and cheap. 

Dont get the FX6350, but grab the FX8320 for arround the same price, its totaly worth it. But its depending on your current motherboard.

So which motherboard do you have?

About a psu, 400W is tight but "if its a decent one" it could do the job for now basicly. But everything arround 500 is more then enough for that setup.

I'd go 6300.  If your power supply is of high qualitu and your motherboard is good, then a 8320 is doable.