the nice thing about garage band is you can use it as a multi track recorder, or as a loops/samples program. it nicely supports multi track input from a few cheap devices, so that's kinda nice also.
Plus, the new version that just came out has some really good "virtual lessons" (yeah, I know that sounds like every other terrible/unusable virutal lesson software in the past, but this is like "wow, they took all the dispeate good elements of existing software and combined it in an intellegenet very well produced way.)
also... I'm surprised you like stacks. You seem like the demographic to complain about it. I personally have not found it a value add, but maybe I'm just used to the previous workflow.
Also, I know of sub $100 USB => DVI devices that let you hook up 4-6 additional displays so you can have a giant extended desktop running off anything from a mac mini to a mac pro without messing with video cards. Let me know if you want to hear more.
Also, I am following you on twitter.
let me know if you have garage band questions. Bobby and I got pretty pro with it, using basically the same setup you seem to have right now, where all your effects are processed external to the computer.
Did i mention we have a new album on iTunes??? http://itunes.com/chojimoji/dontfeedthedinosaursjesus