Mr Drummer :
Thank you for that info. I've got a "Asus GTX770 OC" atm. This is the complete spec of my current rig btw:
Antec 300 + Noctua S12-1200 (120mm)
Asus P5Q-E, Intel Q9550 (OC 3.4ghz) + Noctua NH-U12P
8GB DDR2: Corsair TWIN2X 6400C4DHX
Crucial BX100 250GB + Intel 530 Series 120GB
ASUS GTX770-DC2OC-2GD5
Yeah i'm on a budget and thinking alot about what would be the best ugrade where i'll see a significant improvement. This second hand alternative is the best i've come across so far. But if i would be better off getting a upgrade based around the i5 4690K i'll just have to wait til i get that kind of money.
The 3570K is a beast of a cpu and performs well. I own a 3570k that was paired with a GTX 770 till two weeks ago when I finally upgraded to a 980ti. In gaming you will see little if any between the 4690k and the 3570k. Im talking 3% or less in gaming, were are not talking synthetic benchmarks which ppl like to toss around like the word of god. How do I know cause my wife has a 4690k with GTX 770. We played the same games and there is zero performance in 99% of the games. She would get 2-3fps more in Assassin Creed Unity but outside of that they performed the exact same. Im talking Witcher 3, GTA V, Metal Gear, Crysis, Heroes of the Storm, Dota2, Ark Survivor Evolve and so on.
Don't spend more than you need to, go with the 3570K. It should over clock to 4.2 with out changing the voltage with a Z77 motherboard. Thats pretty standard OC on a 3570k with out voltage changes. If you comfortable upping the voltage a little you can easily hit 4.5ghz but the notice in performance isn't worth it my opinion.