Where To Start?, Listening to my creation Options

[Mr Toner]

I finally upgraded to Sibelius 3 for music notation; I arrange music for instrumental and vocal ensembles. I'd really like to be able to get a better idea of what the arrangements will sound like, instead of relying on the software sounds in Sibelius.

What exactly do I need to be able to play better quality sounds? I have a PowerMac G4 (Sawtooth), but I don't have a keyboard (since I don't play one). I'm guessing I need a MIDI interface and a sound module of some type, plus powered speakers or a stereo system.

I'm looking for an inexpensive solution, but something that will still sound good.

[kaboombahchuck]

It would probably be cheeper to virtual, rather than going the sound module way.
Find out what plugins Sibelius supports, then check out the software section of this site, and find a virtual sampler that will do. Might be a good idea to get one that supports sf2. files (sound fonts). There also a number of virtual synths out there.
As far as listening to the playback of the music, it just depends on how much you want to spend. It might be a good idea to get a set of good computer speekers , with a sub.