Used to be that YS Tech was the sole maker of 125 cfm+ 120mm's. Dunno if this is still true. According to millisec.com,
they recommended the 108 cfm Sunon 120mm over the YS Tech, as it was a better quality fan. I also don't know if that is gospel, or not.
Panaflo's seem to be considered the best case fans.
I have two of the 108 cfm Sunon 120mm's in two boxes. They've worked well for ~1 year, and I have no complaints. The capacity of the case fannage you need depends on a lot of variables. As a rule, an Athlon box needs 100 cfm of throughput, and that's when not overclocked. 150 cfm is appropriate for an OC'd Thunderbird machine. It's said that more than 150 cfm through your case is a waste. I don't know if that is gospel, either.
The 108 cfm Sunon 120mm's are loud. The ~125 cfm 120mm YS Tech's are LOUD. If you wish to move a lot of air through your case quietly, two or even three(for an OC'd K7 box) low volume 120mm's ~65 cfm- need to be used.
Keep in mind: 120mm intake fans
must be filtered. The inside of your box will look like the Sargasso Sea in six weeks of 24/7 with no fan filter, substituting brown for green of course.
Reliable cooling specialist etailers I've dealt with are:
www.millisec.com ,
www.1coolpc.com , and
www.2cooltek.com . My personal fave is Millisec.