I'd love to get the ATI card with my new mac pro, but am always nervous about fan noise on the higher end cards. Some PC reviews of the card say that it's not exactly quiet, but Apple, in the past, has worked with the graphics card manufacturers to dampen the noise on the Mac edition of certain cards. So....how is the 4870 fan noise? In particular, can you hear it over your computer's own fans when the Mac is idling? And does it noticeably ramp up when you're doing some more demanding work? Thanks much!