I also agree with cirdec, the Sennheisers are good in general, don't have specific experience with RS 120 but I'd believe him. You can always check some reviews on pcmag or headphonesaddict to see what other people are buying and saying about certain models.
I also don't see any problem ordering from Amazon, I ordered many times and never had any problems, just make sure you buy the right model for where you live. So If you're from Europe you need different plugs than if you're from USA.