You won't be able to carry your RAM over so everything can be sold to help the cause.

Something like this is what I'd probably go for:

PCPartPicker part list / Price breakdown by merchant

Type Item Price
CPU Intel - Core i5-8600K 3.6GHz 6-Core Processor $279.89 @ B&H
CPU Cooler CRYORIG - H7 49.0 CFM CPU Cooler $34.89 @ OutletPC
Motherboard ASRock - Z370 Extreme4 ATX LGA1151 Motherboard $156.98 @ Newegg
Memory Corsair - Vengeance LPX 16GB (2 x 8GB) DDR4-3000 Memory $194.99 @ Amazon
Prices include shipping, taxes, rebates, and discounts
Total (before mail-in rebates) $676.75
Mail-in rebates -$10.00
Total $666.75
Generated by PCPartPicker 2017-11-03 13:26 EDT-0400

You can get a beefier cooler to get right at the $700 limit.

The 8600k is probably the best gaming chip on the market right now in terms of the performance you get at the price point.

/r/pcmasterrace Thread