After the responses I had last night I decided to try and achieve a stable 4.8ghz. It took a lot of tests to get it. Last night I run Prime95 blend for 6hrs without error. Tonight I'll run a much longer test but if I can get to 15hrs I'd be confident to leave it at that spec.
At first I tried increasing multi to 19 and leaving the FSB at 255 but max temp went through the roof as I had to increase vcore from +1.00 to +1.25. I tried Prime95 and within 2 minutes temps went over 65 degrees ++ and vcore went high as 1.51 with LLC on auto so ended the test.
Using the same settings I tested it with every LLC option available and when at the 4.8ghz range I could drop the vcore setting from +1.25 to +1.00 when using LLC extreme mode but temps were still a bit high although starting to drop.
I then tried increasing FSB from 255 to 260 and decreasing multi back to 18.5. This reduced the core speeed from 4845mhz to 4810 mhz and I tested this with all LLC options and found much the same as previously mentioned but using a 260 mhz FSB and keeping the NB and HT at 2340 mhz. The max temp went to 64 during 6hrs of a Prime 95 blend test. Temp settle to 60-61 degress which is still on the high side. In the end I was so surprised at getting this to be stable as a 255 FSB using auto LLC I found that I would get rounding errors in Prime95 when NB was just over 2400. Because Of this I felt I could only get a higher OC by using multi and keeping FSB at 255 and NB and HT at 2295. The 4.81 OC using FSB resulted in much better performance than 4.84 that used a 19 multi and 255 FBS.
I've run a couple of benchmarks and everything has improved and stable in games. There was a big improvement to the physics score for the 3DMark11 performance test
4.71 3DMark Performance - http://www.3dmark.com/3dm11/6757401
4.81 3DMark Performance - http://www.3dmark.com/3dm11/6764664
I still plan to add some additional case fans to try and reduce temps. If I'm able to get reduction of 4-5 degress I think the 4.81 OC would be ok for a 24/7 spec. Also i've been able to get a better OC and lower temps using the Noctua NH-D14 than a Antec 920. A lot quieter as well and no annoying ticking noise from the Antec pump
In the end here are the settings I used to achieve the stable OC at 4810 mhz
CPU Clock: 4810 mhz
FSB: 260 mhz
NB Clock: 2340.1
HT Clock: 2340.1
Max temp Prime95 (blend test) was 64 degrees but settled at 60-61 degrees.