Lower graphics results on my overcloked machine

[spike15_mk]

I still do not get it. First i thought that the PSU was the problem(I previously had Deluxe 700W). So I bought Cooler Master Silent Pro M 1000W. But still when I test(with 3D Mark Vantage) I still get lower results on graphics even though I overclocked my i7 on 4.0 stable(checked with Prime95 for 6 hours, and memtest 86+ all show pass). So what could be an issue here?. This is relay strange. I would understood if the graphics remained same, but lower? It does not make any sense?
Please advices needed?
TnX

My system specification:

Asus Rampage II extreme X58

Intel i7 920 overclocked on 4.0 GHz with 1.25 V and 35 C in idle(on maximum load it never exceed 65)

6 GB DDR3 Kingmax 1333

Nvidia 9800 GT 1 GDDR3 1.5 V

1 TB Samsung 32 MB Cache

500 GB WD 32 MB Cache

HAF 922 with fans in every place

CPU cooler: Cooler Master V10 TEC cooling

PSU: Cooler Master Silent Pro M 1000W

 

[Lmeow]

Well, I'd check whether the overclocking actually affects your gaming performance - the overclocking may still have boosted your gaming performance, even though the benchmark says otherwise. Check your temps though, if you pushed your card too hard, it may be throttling back during the benchmark thus resulting in a lower score.

 

[spike15_mk]

Well I did not think about that. I will have to check. Also I planned to overclock my GPU. But a little overclock , nothing serious.

Peace