I cant seem to spend over $1k on a rig and not have it be extremely powerful. Rocking dual x5650's, HD7950 @ 1GHz, and 24GB ECC DDR3 for ~ $1000. I found a new 750HX PSU on ebay for $70 and all of the RAM (+2TB HDD) out of an old server I payed $420 for. Each Hexa-core Xeon was $95 a piece and the MOBO was $125 I believe. I payed $350 for the HD7950(new,) and $75 on a huge sturdy case. My $650 used gaming laptop also runs BeamNG on maxed settings with no problems whatsoever.
A GTX 960 is also very nice if you need to cut on some cash, most games running sweeeeet on ultra Not saying its better of course, but maybe you could do 2 960's over 1 970? 0.0
Well here's my 2 cents. 8 GB ram is really all you will need and you also don't need a i7 to run this game. I've got a i5 4460 and all I've had to change was the stock cooler.