Advice on overclocking my i7 875k on an Intel DP55SB

Just after some help really, I'm looking to get the best out of my setup and am struggling with the BIOS on my Intel DP55SB. I don't understand how each of the features affect other aspects of other features.

I'm not a total noob to the overclocking scene but this board is really awkward in my hunt for a decent 24/7 overclock.

I'll grab some screenshots of the BIOS a little later as I'm currently using said machine, but in the meantime does anyone have any tips on overclocking an 875k in general? I had it running @ 24x160 on 4,3,2, cores and 25x160 on 1 core @ 1.3V. I had weird issues running a 10x multi so now its currently its running at 18x200 on all cores with a 8x multi and all is fine @ 1.3V. The QPI link is now at a much better 3.6GHz which I'm happy with. I'm hoping to get 4GHz on all cores and maybe a higher speed when running on 1 or 2 cores.

My setup:

Intel DP55SB
i7 875k
Antec Kuhler 620 with 2x yate loon D12SH-12 fans (push/pull)
16GB (4x4GB) of Kingston DDR3 LoVo 1600MHz @ 1.35V
Sapphire 7950 @ 1GHz/1.25GHz (core/mem)
120GB OCZ vertex II SSD
1TB Samsung HDD
620W OCZ 80+ bronze PSU
All housed in a Silverstone PS07 with two Enermax 120mm TB silence fans on the front intake.

The 875K... well at least it is unlocked and allows higher memory ratios and reducing latency should yield some performance increase.