The "device or software I use to create them" being the hardware/software sequencer that you use to record and manipulate MIDI data relaly has nothing to do at all with the quality of the sounds themselves. You are at the mercy of the quality of whatever devices respond to those captured and mnipulated MIDI messages. The synths on consumer cards like the Sound Blaster are just plain not very good compared to a nice external Roland or Korg or whatever. I mean, whatta ya want for $75?
However, you can get markedly better sound out of some of those cards, in two ways. Method #1 is restricted to only certain cards, those that support the Sound Font or DLS standards. These are sample formats that can be loaded up as sound sets into the computer's memory, and played through the sound card's hardware synth. Since you can use up to half of the available system RAM to load sample sets, they can be large enough to be of excellent quality. SB Live cards and the new Audigy ones support Sound Fonts, and I think Terratec cards might too. Turtle Beach's Montego II card supports DLS.
Method #2 is not limited to particular sound cards -- it's using a software synthesizer/sampler, like Gigasampler and many others. These can be remarkably good, but they do tax your computer's resources and can reduce the number of tracks and/or the number of effects plugins that you have at your disposal while recording...
