Not sure why that post "If" popped up.
You could build off the current board. The X79 platform is not as expensive as the X99 platform, as it still uses DDR3 RAM and you already have the other expensive part, the RAM. You can also grab the cheapest Ivy Bridge Extreme processor for about as much as the top Devil's Canyon processor.
Here are some suggestions if you feel you can sell the Rampage IV Extreme for a profit, these suggestions are based on total price excluding a case or optical drives. As long as the case supports ATX sized motherboards and is at least a mid-tower that has space for an 11" graphics card - be warned, I don't know how long the R9 Fury will be, it will be bigger than the Fury X no doubt - that case should work.
$680:
CPU: AMD FX 8350 ($170)
CPU Cooler: Cooler Master Hyper 212 EVO ($30)
Motherboard: Asus M5A99 Pro ($120)
GPU: AMD Radeon R9 380 ($200)
PSU: Corsair CX750M ($80)
RAM: Crucial Ballistix Tactical 2x4GB DDR3 1600MHz CAS Latency 8 ($54)
HDD: Western Digital Blue 1TB WD10EZEX
Note: Newegg has a combo where if you buy the motherboard, CPU, and power supply in this kit, you get a $22 discount.
$900:
CPU: Intel Core i5-4690K ($240)
CPU Cooler: Cooler Master Hyper 212 EVO
Motherboard: ASRock Z97 Extreme4 ($100)
GPU: EVGA GTX 970 FTW ($325)
RAM: Crucial Ballistix Tactical 2x4GB DDR3 1600MHz CAS Latency 8 ($54)
PSU: Rosewill Hive-650 ($64)
HDD: WD Black 1TB ($75)
CPU: Intel Core i5-4690k ($240)
CPU Cooler: Cooler Master Hyper 212 EVO ($30)
Motherboard: ASRock Z97 Extreme4 ($100)
GPU: Asus STRIX GTX 980 ($500)
$1400:
CPU: Intel Core i7-4790k ($340)
CPU Cooler: Cooler Master Hyper 212 EVO ($30)
Motherboard: Asus Z97-A ($140)
GPU: AMD R9 FURY ($550) *Make sure this is the "Fury", not the "Fury X". These cards will be out soon - the Fury X will be out Tuesday and the Fury will not be far behind it.
RAM: G.Skill Trident X DDR3-1600 CAS Latency 7 ($135)
SSD: Patriot Blaze 120GB ($50)
HDD: Western Digital Black 1TB WD1003FZEX ($75)
PSU: Corsair CX750M, Cooler Master G750M, or EVGA SuperNOVA NEX 750W ($74)
There are two reasons other than overclocking why you'd buy a ROG board: Quality components, and eye candy. I have a ROG Maximus VII HERO and it is the prettiest thing I have ever seen. It's basically a quality work that I didn't want to cheap out on. And you already have it, and you got it for cheap.
$700 pre-GPU
CPU: Intel Core i7-4820k ($320)
CPU Cooler: Cooler Master Hyper 212 EVO ($30)
RAM: G.Skill Trident X DDR3-1600 CL7 2x8GB ($105) *On sale for $30 lower than usual
HDD: WD Black 1TB ($75)
PSU: Rosewill VALENS-700M ($90)
Case: Rosewill Armor-EVO ($72)
The GPU will vary based on how much money you have available. Keep an eye on whichever ones you might be able to afford. Since you have to dump so much into the CPU (that is the cheapest one that fits the Rampage IV) I'd recommend, at least in the near future, getting a card worth more than the CPU.
$200: AMD R9 380
$325: GTX 970 cheapest models
$390: EVGA GTX 970 FTW+
$500: GTX 980 cheapest models
$550: AMD R9 Fury
$620: Asus GTX 980 ROG Matrix
$650: GTX 980 Ti or R9 Fury X
$700: Aftermarket GTX 980 Ti (Gigabyte G1 Gaming, Asus Direct CU III, Asus ROG Matrix)
When you look at a graphics card, it should tell you what power pins are required. If the card requires two 8-pin connectors or more, then you need to buy the Rosewill Hive-750 instead of the Rosewill Valens-700 to keep plenty of breathing room. I know offhand that the Fury X requires this, the Fury likely requires this and aftermarket GTX 980 Ti cards with big aircoolers may require this. The Hive-750 costs the same as the Valens-700 because it has lower efficiency.
Something else to keep in mind is that the Fury X uses a liquid system. While it's probably maintenance free, accidents do happen.... which has partly kept me from LCS units in the past. However the Fury X is demonstrating itself to be an interesting chip, perhaps more so than the 980 Ti.