[bglenn09]

For the features you're looking for, the other commenters gave you the two best-bets that I'm aware of. Personally, I use Visual Studio 2010 and really like it, primarily because of the multi-pane, multi-monitor support. In other words, I use it as a really fancy text editor. I do code heavily in ExtJs. For integrated debugging with ExtJs, Firebug is totally indispensible.

Getting started with Ext can be hard. I'd suggest starting with the demos and tweaking the code from there for your needs. The API reference online is very useful. StackOverflow is about on par with the forums for questions.

Good luck.