Overclocking crossfired 4830's

Hey, so I have this setup and I am trying to overclock my 4830's.

Processor: amd pheom II x3 720 2.8 ghz
MotherBoard: asrock a780GXE
Ram/Memory: G.SKILL 2x2GB ddr 1066
VideoCard(s): 1 Powercolor 4830, 1 Sapphire 4830
Case: coolermaster rc-690
PowerSupply: Coolermaster 750W real-power-pro

So here's the deal, I am using ati overdrive to check temp and overclock, and I have gotten this so far.

695 Mhz core clock on both, and default 900 mhz memory on both (haven't overclocked that yet) and I used crysis benchmark tool to check for artifacts.
The powercolor video card idles at 37C and the sapphire idles at 43C, while running crysis benchmark the powercolor goes up to maybe 47C and the sapphire goes up to 55C, so all is good here.

While using crysis benchmark tool I see no artifacts, but if I test it with furmark I see this bluish lines (hardly knoticable) and when running furmark it crashed and only made it to 1:47 minutes into the test, and ATI thing popped up saying it reset somthing and had an error. I emmediately checked the temps and the sapphire video card had hit about 78C and the powercolor had gone about 62C, so temps are still OK, but not great. I backed off 15 mhz on both cards.

since crysis runs fine am I ok with the original 695 mhz? even though furmark crashed and had little blue lines?

Thanks everyone!