Doubt you'll get much more out of it if it's rated at 6-6-6-25!
If you want to get it past 800mhz then it really needs to be rated at Cas4. I went thru loads of cas5 ram that wouldn't oc more than 50mhz. in the end i just bought some cas 5 1066mhz
No,his timings arent 6-6-6-18,sometimes(I had this too)BIOS sets the timings of the RAMs to a number which isnt for them.u have to set them manually for example my RAM was set @ 5-5-5-9 in BIOS(original is 4-4-4-15) so i set them myself.