The Devil's Canyon chips are specially binned, high-performing Haswell processors with a higher-grade package and superior thermal interface material between the die and the integrated heat spreader.
The quad-core i7-4790K has 8MB L3 cache and HyperThreading, it's clocked at 4.1GHz and has a 4.4GHz. Its pricing is around $370. The i5-4690K on the other hand is a quad-core model without HyperThreading, it has 6MB L3 cache, a 3.5GHz core clockspeed and a 3.9Gz Boost. This version will cost you around $250. Both versions are designed for overclockers - they're fully unlocked.
The Pentium G3258 on the other hand appears to be an interesting chip for overclockers on a small budget. Priced at around $80, this Haswell-based dual-core chip has a frequency of 3.2GHz and 3MB L3 cache. It lacks HyperThreading, Turbo Boost and the AVX instruction set but offers an unlocked multiplier.