Not built a machine in 4 years, but a great resource to you is
http://www.passmark.com/baselines/top.html I linked the top benchmarked systems on there, but the top of that page also has benchmarks (tabs at the top) specific to CPU, drives, Ram, GPU, etc. These scores are uploaded by people benchmarking their machines using Passmark's software, and the top machines have a common theme to CPU/MB/RAM/Card.
- CPU - Intel Core i7-5960X @ 3.00GHz
- MB - ASUSTeK COMPUTER INC. RAMPAGE V EXTREME
- GPU - GeForce GTX 980/970
All of those systems are overclocked, which is not something I would
not recommend as it is not as dramatic as many think and causes excessive heat to the CPU (which will damage it over time!).
Just bear in mind... regardless of how "high end" your machine is, you will still need an audio interface to do any serious audio recording (so budget for that one too).
Also realize you do not need "top of the line" (so check the benchmark vs price for components) as my machine still runs at <30% CPU on the most intense things except for encryption/video rendering. An SSD on the OS is recommended (be sure to research proper setup and maintenance of them).
Bottom line... research a lot and ask a lot before building/ordering.