OK, so I got two systems, and a few ram sticks. Both systems are kinda old, but with RX 580 8GB on both, and SSDs.
So, which one should be the best to pair with an HTC Vive?
>W3680 4GHz (6/12, it's about 20% a lower in single, but 30% faster in multi)
>i7 4790 stock 16GB RAM 1600MHz

And then, if the first one since it has a better multicore, I have a few ram combinations
>16GB dual channel at 1333MHz (2*8gb)
>12GB triple channel at 1333MHz (3*4GB)
>15 (3*4GB+3*2GB) or 18 (3*4GB+3*2GB) at 1066MHz
Even second hand ram is expensive right now, but if I can I'd try to get a single 4GB so I can use 6*4GB or a single 8GB stick to use 3*8GB, which would be the best.

I might swap a mobo and use a z87 with the 4790 to OC the RAM and the CPU a little, and i think that would almost match the W3680 in multi, so it should be the best one.