Using Aria is a good idea, just have to set it up for each tune if the instrumentation changes. As Mario has said, GM sounds are just not very good. OK for a quick listen to get the idea of a style maybe, but only just that. Really not good if you want to do something professional. IK Multimedia was having a great sale on their Total Studio Max 2, which includes Sample Tank 4 and a huge library of great samples, as well as Amplitube 5, T-Racks 5, more than I can remember. Quite easy to learn to use as well. Their licensing and authentication system can be confusing and there are a multitude of downloads to do when you purchase, but in the end it is worth it.

My wife asked if I had seen the dog bowl. I told her I didn't even know he could.