add OEM for $99.99 and a $50 case then will be $600. Just unsure if this is the best option or if I should build something else. My brother has never had a new computer. Normally gets my old ones after there a few years old.
The H61 motherboard is very low-end, but you don't need more than that for your usage. i3-2120 is also enough.
RAM: you can go with a 4gb stick, kingston/corsair/mushkin ddr3 1600mhz (1.5v ideally).
GPU: good, and good price.
With the small motherboard, and your type of usage you might be able to get a micro-atx case (make sure your graphics card will fit.
The PC i built for a friend for SW:TOR had a i5-2500k, Radeon HD6970 and 4GB memory, running perfectly (was overkill, and he wanted it to be "futureproof").
If your brother is going from an older computer to this, he will be very happy. The next step would be getting a SATAIII SSD such as an OCZ Vortex 3, that'll send his head spinning (just bought two for 150$ CAD each!).
Don't get the Z68, it's a waste of extra money, save a little and get the Asrock H61 U3S3 that you were going to get. The reason I say this is you don't plan to overclock and you don't plan to SLI/CF either so no need for the Z68. Plus the capabilities you'll use are basically the same.