I am so tired right now, but here goes...
You need different things for different things to do.
Reason, FL, and logic are sequencers. They make the music, edit midi, edit audio (not ALL of those 3 actually), etc. Logic pro is highly professional actually for orchestral music, and what a lot of pros use in the film music business (or computer game music).
Other sequencers: Sonar, Cubase, Reaper, Audacity, Logic, Reason, Fruity loops. Ranging from free to hugely expensive
Then you need something to
play sounds.
This can be a synth, or module which will
create sounds via various ways.
Another way is to use
samplers. They will get a captured recording of an instrument, mapped on the keyboard, so everytime you hit a key, you will hear that exact recording. (<-short explanation I know).
Major samplers: Giga studio, Kontakt, Halion
Then you need actual sounds to use in your sampler
They range from pianos, to synths, to choirs, to orchestral, to drums, to whatever.
Major companies making orchestral samples: Garritan, EastWest Quantum Leap, Vienna Symphonic Library, Sonivox (Sonic Implants), Kirk Hunter.
What I personally use:
Cubase3
EWQL Gold, Gold xp pro
EWQL Symphonic Choirs
Pianoteq 2
Synthogy Ivory
Drumkit from hell superior
Manytone Manybass
EWQL Vapor
EWQL Adrenaline
Bela D. Media DIVA
and various smaller stuff.
I also use a very early version of Finale for notation.
If you plan on actually
buying, cause for some reason I'm not sure about that, both Kirk Hunter and Garritan have DEAD cheap orchestral libraries. Also reaper, is a good shareware (=almost free if you don't care to give the asked price, they won't hunt you down) sequencer.
If you want to get anything else you either get cracked copies (

) or pay dearly...