Just a few things I notice:

1) Your motherboard is overkill for iRacing. You could go with a motherboard like this one and get the same quality of play. From talking to computer people, once you get past the $150 range for a motherboard you really are splitting hairs as to noticeable performance gains. Might save $80 or so.

2) You included a sound card in your build. Most motherboards have onboard sound cards. So unless you're doing things above what iRacing is capable of, the motherboard has all the sound you'll need. So that could save you $34.

3) Computer case opinions seem to vary. But if you aren't totally in love with that case then take a look at this one. I just bought it and it seems to be a pretty good case. Lots of room inside and plenty of space for fans and cooling. It will save you around $62 if you have amazon prime.

So with the $175 you could upgrade to the i7-6700k CPU that is 4.0GHz or you could upgrade to the 1080 graphics card... or you could pocket it. I'm not a computer guy by any means, but the people on the iRacing forum helped me learn a ton when I was trying to figure all of this out. Hope it helps.