you are in the bitcoin subforum, so i'll give a bitcoin answer: there is no pc you can ever build that will mine bitcoin profitably. Even worse, even the best GPU with free power will make about ~20 cents a year at current diff, block reward and btc price. Since such a GPU costs ~$350, it'll take you (on average) 1750 years before you mined enough BTC to pay back your initial investment IF you got your power for free, IF the diff didn't rise, IF the block halvings were removed with a hardfork and IF the price didn't drop.
Here's an auto-updated list of some non specialised mining hardware, it's hashrate, it's power consumption and it's revenue @ certain fixed power prices:
https://www.mocacinno.com/nonspecialisedmininghardware.phpBottom line:
- you can't mine BTC profitably with a cpu (any cpu)
- you can't mine BTC profitably with a GPU (any gpu)
- you can't mine BTC profitably with a cellphone (not with it's cpu, not with it's gpu)
- you can't mine BTC profitably with a botnet (a botnet with 1000 PC's with an i7 will make you less than $10 a year if you run them at 100% load 24/7 for a full year)
- you can't mine BTC with a supercomputer (since a supercomputer is basically just a collection of hundreds of 'nodes', which are basically small, stipped servers)