Disclaimer: I play in orchestras regularly.
To hear a great orchestra perform live is an awesome experience, not really duplicated by any other medium. Musicians of the world's best orchestras are masters of their craft, who have devoted their whole lives to perfecting their art. Listen to the Berlin Philharmonic, for example, and you hear nothing short of perfection. An orchestra judged by its merits and musical product alone is easily sub-zero.
The problem is, in today's society orchestras are associated with snobbishness and the rich. Part of this is because classical music in general is instantly dismissed as snobbish and for the rich, which is because the audiences who typically attend orchestra concerts and listen to classical radio are generally stereotyped as "old people". This isn't really deserved, but what is deserved is snobbish criticisms coming from what has now become accepted as standard concert etiquette.
The orchestra members are wearing tuxedos and formal gowns, the audience is also dressed nicely, the concerts take place in (usually) extravagant concert halls, and the audience is expected to be completely silent. You get scowls from everyone if you clap between movements of a piece, or even cough. I will admit that when I'm at an orchestra concert (whether performing or in the audience) I want the audience to be completely silent, but it doesn't give the orchestra a good reputation with free-spirited youth and people who are used to yelling and screaming whenever they want at rock and pop concerts. There are designated places when you are to applaud obligatorily (at the ends of pieces, when the concertmaster walks out, when the conductor walks out).
American orchestras have been in dire straits financially in recent years, due largely to being out of touch with most of the public, and several major orchestras have or have nearly declared bankruptcy, locking out all of the musicians in the process. To rectify this, orchestras have been programming concert series geared towards younger concert goers. More casual venues, more recognizable music (film music, etc.) grouped together with classical standards, and the like. the snobby stigma may eventually be lifted from the orchestra. I definitely hope so!
All that said, the orchestra is responsible for much of the music that people would define as sub-zero. The best movie soundtracks, for example. Modern video game soundtracks. Orchestras have been employed by groups of all genres, including extensively in progressive rock and metal.
So, although the stigma is there, I can't classify the symphony orchestra as anything but sub-zero. It's the classiest, most polished musical ensemble in the world, that also requires the most dedication and musicality and is capable of the widest range of emotions.
