A headphones quality is not determined by bass, its generally determined by build, comfort, and audio quality. Bass is a personal preference and is common nowadays with all the popular pop, hip hop, and rap songs out there. If someone says bass is what makes headphones good they haven't tried anything but Beats. As Gam3r01 said a balanced sound is good for all-round use and can also be tuned for more bass, treble, or whatever you like with a software equalizer.
About the 5.1 I think you're mistaken, the HD 439's are stereo. Anyways continuing the topic pretty much any headphone or headset that declares its 5.1 or 7.1 is virtual with a few exceptions. Virtual surround is pretty much stereo tuned to sound "3D" and is sorta based on the placebo effect (search it up if you don't know what it is). There are a few headsets that have true 5.1/7.1 but the audio quality of them is poor, with all the small drivers jam packed into a earcup.
Beats is just overpriced $30 headphones, which are induced by celebrities, sports stars, and Apple - that's why they are hated by audiophiles.