Well, it depends on some things you've not detailed.
What point are you starting from. What sort of 'nice orchestral sounds' are you thinking of.
Maybe your PC has some soft of sound facilities already? Incl audio output?
Maybe you could use a soft synth, so you don't bother with extra sound card or module. A soft synth that can load samples maybe better than many modules (except the most expensive ones)? I think soft synths can still play midi files. I'm sure there are soft synths you can download for free. This will get you started, saving the cost of further sound source.
Geoff