Upgrading graphics (and memory) on HP H8-1559

[paleven]

Hi,

I am currently looking to upgrade the graphics and performance of my HP H8-1559 pre-built computer. The specs are here:
http://h20564.www2.hp.com/hpsc/doc/public/display?docId=emr_na-c03668430-9

I am using this computer for gaming (ie. Starcraft 2) and for CAD and 3d modeling which I do for work, and is therefore my first priority. I want to upgrade both the graphics card and the memory.

GPU
For the graphics card I am unsure of which one specifically. I am thinking about this one:
AMD R9 270X ($229.99) http://www.newegg.ca/Product/Product.aspx?Item=N82E16814150692&cm_re=r9_270x-_-14-150-692-_-Product
I am open to any suggestions. Is there merit to using an AMD GPU to go along with my AMD processor? Is the 270x worth it over a cheaper card?

Memory
I also want to upgrade the memory. Currently the computer is equipped with 2 4gb DDR3-1600 cards. I am thinking of adding these:
http://www.newegg.ca/Product/Product.aspx?Item=N82E16820231568
Does it matter if I have 2 4gb and 2 8 gb memory cards?

PSU
And I have read that I will need to upgrade my PSU as well to support the GPU (as the current one is only 460w), and was thinking of going with a 600 W PSU. My current choice is this one:
http://www.newegg.ca/Product/Product.aspx?Item=N82E16817139028&cm_re=cx600-_-17-139-028-_-Product

My budget is about 500$ (in Canada) and the memory and PSU combined is about $230, which means I would like to stay less than $250 on the GPU. Any recommendation for the GPU are welcome, and if you see any issues with my memory or PSU choices, please let me know. Any and all help is greatly appreciated.

Thank you all for the help in advance, I feel well out of my comfort zone trying to decide all of this.

 

[Emerald]

To avoid complication, replace the memory and do not use both.

For a chance to both work together all the timing and latency values need to be the same.

GPU should work

I would recommend a PSU of the following Seasonic, Antec, XFX, Superflower, Evga(b2,g2,p2), and Corsair(hx, hxi,ax,axi)

Here is a list of PSUs by tiers. I usually stick with Tier1 or Tier2.

http://www.tomshardware.com/forum/id-2547993/psu-tier-list.html

 

[avenseth12]

I like your choices. As said, just remove the old RAM and install the new. Your GPU choice is a good upgrade and good call on the PSU, it will be better for you in the long run. Don't change anything.

 

[paleven]

Thank you both for the answers. Follow up question after doing a bit more research on graphics cards. Is it worth spending a little more to get the r9 280? I can get it for nearly the same price as the 270x.
http://www.newegg.ca/Product/Product.aspx?Item=N82E16814150705&_ga=1.221661976.1402782522.1424706515

Thanks again!

 

[avenseth12]

It cant hurt - I would buy if for same price