If you look at the main AnandTech site, most cards now are very quiet under low loads, it's only for high-end gaming like Crysis 2 that the fan ramps up.
That said, some non-reference designs can be much louder, such as Zotac making noisy Geforce cards. And sometimes a vendor messes up the automatic fan speed control in their BIOS so it runs cooler but much louder than needed.
For the CPU, intel Sandy Bridge (i5 - 2500K) is going to be quieter than AMD since it offers much higher performance per watt (and overall performance). Less heat = less cooling = less fan noise.