It's amazing to me, and I don't mean to belittle you at all, how often this question gets asked. The best thing for making Flash is Flash. Believe me, there are competitors out there with impressive features, but you won't find their players auto-bundled into your new computer purchase. Flash is just kind of an accepted standard now.
As for audio, I'm not sure how you like to work. Are you an old school step-writer, or have you embraced digital chicanery all the way. There is no right or wrong answer. For my musical production, I use Sonic Foundry Acid for arrangement, Sonic Foundry Sound Forge for individual editing, Propellerhead Reason primarily for synthesis, Supercollider for algorithmic anomalies, Molar (and a pile of other open source programs for Monome 256) for live sample editing. That's my way though. Your way is probably totally different, and it's OK. I know lots of people who make amazing things on Fruity Loops (a program which defies logic to me). Then there's the Mac crowd, with all the Ableton/Steinberg stuff. It really depends on what you want to do, and what system you are working with. Ask me. I do this shit for a living, all day.
:D
