850 Budget Gaming PC

The xfx 550 core edition is a fine psu, it's a seasonic oem psu.
Well, if you can't wait then get the 7870XT from sapphire.
If you need to shave some, get the psu here : http://us.ncix.com/products/?sku=59615&promoid=1257
Ram : http://us.ncix.com/products/?sku=74758&promoid=1321
Change the psu for the hyper 212 plus.
This might allow you to get the sapphire 7870XT.
But i rather wait for the powercolor for the price, it will be back soon.
Check the auto notify and it will alert you when it's back.
 


Remember that you can get the xfx psu on ncix us, in amazon is out of stock, you can get the ram there for 1.5$ less, and with the psu it will be more than 100$, so you'll get free shipping, ncix us is a reliable website for parts.
You might just look for the powercolor till then,the promo ends on Friday and it will probably be on stock in just two days, and save more than 40$.