The best approach is what suits you the best.
SID sound cards are an interesting subject. Sweet things for anybody to own for sure, and if it gets your creative juices flowing, certainly worth it. (For an example on how to not use SID hardware, see
Timbaland.)
What about chiptunes? Be more specific. Whether we like it or not, the term is now more wide-ranging than ever. It can mean many things, I think it means all of them at once. The key is the easily generateable basic sound waveforms we all know and love from our belowed 8-bit systems,
and things that sound like that.
Do artists draw everything themselves? No. In many cases that's not even an option and you're stuck with whatever parameters you can control on a sound chip. If you're using a sample based tracker, you have that option, or you can use generators, synths, whatever to produce the sound you like. Using a VST, why not? Enforcing specific platform limitations might become harder with more advanced tools but that's not always the point either, you can just make chip-influenced-whatever-tunes (still falling under the broad definition of chiptune). Just as there is no set destination, there is no one path there. You decide what you want to make and how. If it's not working, you'll know, or somebody will come and tell you.
The classic Amiga sound you're probably thinking of is not a chiptune sound. The hardware specs contribute to sound quality but since it's already all sample based and
realistic the sound is defined by the unforgettable, cheesy, lovable and godawful '80s/'90s samples. Dig in:
http://aminet.net/search?query=st-%3F%3F.lha
