Hrlyrdr22 :
My wallet cried the minute I saw the multiple SSD's
Why would a music producer need a 4-way SLI TITAN X?
Sorry, everyone. My officemate does things like this sometimes when I go to meetings or step away. So just consider my account's post above a silly joke.
But to answer your question, you'll need to first find out what your software can access. How many CPU cores can it address, and can it use a dedicated GPU? The Xeon vs i7 thing is kind of a non-sequitur, since both perform very similarly. The main thing that would benefit you on an i7, over a Xeon, is that the "K" and "X" versions of the i7 chips will let you turn up the speed if you have enough cooling and power by overclocking the chip. That will help boost your CPU-driven tasks. But the difference won't be huge, and you should really focus your software's ability to leverage higher-end hardware for your audio workflow.
Knowing your software's potential will tell you whether it's worth getting a 4-, 6-, or 8-core CPU, and whether it's worth spending money on a fast GPU.
Without knowing ahead of time, I would recommend trying to get an
i7-5820k. Most new audio production software can generate many thread commands, and having a 6-core CPU would help. It also is a good price considering the other options. The only two things you need to consider (assuming you can afford the X99 upgrade) are whether you'll have enough cores and PCI-e lanes. The 5920k has 28 PCI-e lanes, so make sure your PCI-e expansion needs won't exceed that. As for CPU cores, the 6 in that CPU should be plenty, but you can always get more if you want to spend a lot of extra money. Adding more makes each one a little slower, however, so you have to keep in mind whether your software benefits more from fewer faster cores or more slower cores.
Other than that, be sure and get a big chunk of RAM. Make sure you configure it to either fill the board, or else leave it so that you can fill the board later without throwing away RAM sticks you already bought. If you get an 8-slot broad (for instance) that holds up to 64 GB, you can buy 4 stick of 8 GB each for a total of 32 GB. That would let you buy another of the same kit later to max out at 64 GB. The risk there, however, is that you'd be running two kits. Sometimes (rarely) they don't work together, and people (rightfully) give general advice against mixing kits - even if they're the same make and model. But the only time they haven't worked for me, I've just exchanged them back to Amazon, and it worked fine. It really comes down to your risk tolerance. The only other option to avoid that situation is to buy a single kit up front that maxes out your board.
Good luck!