Hey Pson44, I cannot wait for DIII too! The build Hiya posted is a great build, fits well within your budget and will be great for many more games other than just D3. However, you may find this video of interest too - Diablo III PC Builds
It is a basic overview of the minimal hardware needed to play Diablo III on both the highest and lower settings just for an FYI.
Do you think a $500 dollar build will get the job done on the highest settings with no problem?
I do indeed. If you read the article Diablo III Performance, Benchmarked posted here at Toms Hardware, you can see the various benchmarks that par up with the build in that video.
for barely playing DIII on max $573 (OS eats up $100 by itself).
basically you can take the above build and dial down the CPU and GPU to a i3 2100 (MC has for $90) or an AMD Quad Core (to be safe) Saves $100 and the video card to a GTX 460/HD 6770/7770 card ($130) saves another $40, drop the aftermarket cpu cooler saves $40, Switch to a H61 or AM3+ MB depending on CPU - no savings. go with a NZXT Source 210 case for around $40 from new with free shipping saves $30. then drop the RAM to 4GB ($23 from newegg) saves $17
800 - 227 = $573. (I hope i calculated right) you can build for less using older CPU's and chipsets, but that would be foolish in my opinion.
Personally, if you have the $, Why_Me's build is the best bang for the buck build I have see so far this month - thanks to MicroCenter's crazy prices on ivy/sandy and MB. it will handle way more that just DIII.