Yes, Logic (pro) and Kontakt are good choices, but a little pricey ($500 and $400). A decent alternative is IK Multimedia's Sonic Synth 2 or Sampletank 2. They both run about $200. But, if I was in your shoes, I'd probably go with Logic Express 9. It also goes for $200. And like it's big brother Logic Pro, it gives you access to the built-in EXS24 sampler, can use any other Mac AU or VST, and it's a complete, and pretty sophisticated recording application.