4870 overclocking / crossfire

ive maxed out ati overdrive gpu @800 lame oc
ive tried ati tool riva tuner and rad linker but none seem to register the card.
whats the best software to overclock the card with?
also if i add crossfire (hopefully next month) will my 600 watt psu be able to cope with 2?

I've had good luck with rivatuner. I can't seem to get it to work in win7 but on vista and xp it worked fine. Its a little tricky to get to work on vista so hopefully someone can explain how to get it to work (I don't remember what I did).

800 for the core is a good OC, you will probably end up somewhere between 800-850 depending on if you volt mod the gpu. For the memory I've had 1200 running for a while perfectly stable, never pushed more, but I saw no improvement over stock.

im running xp home,
think ive just for got how to use the oc progs not had a decent pc for around a year lol (old one fried in lightning storm took a year of insurance arguing to sort out)
ill see what i can do with it or try a different version

got riva tuner working now
upto 820mhz gpu so far not artifacts or crashing