I would like to congratulate CS on the amazing soundset they have created for this product.  Not many developers can capture audio like this.  I just wish FS had the capability to handle that deep, rough roar of the engines you hear at the airport.  Unfortunately, FS does not do a good job of that, and so it all depends on the audio design.

One of the best FREEWARE audio packages is one that I use with my MD-83 / DC-9's.  That TRULY gives you the big hardcore sound of those JT's.