If you can find a decent deal on one you might try the xeon 1231v3. It's slightly more than an unlocked i5 but cheaper than the i7. Essentially it's a 4770 without the integrated graphics, 4c/8t with speeds similar to the base clocks of a 4690.
It depends on what games you play as to whether the i5 will offer you a decent amount of performance over what you've got. What motherboard do you have? If it's not a z series doubtful you'll be able to overclock on it so no real point in getting a k series i5 unless it's a decent price. Typically the k series are priced higher for their unlocked multiplier which won't help you much unless you have a z series board.