Bulldozer already does shine in certain things, in some things it beats out Intel. Direct X11 games, which are the newest and sexiest. (BF3 for example) FX-8150s stand right up to I5-2500Ks and i7-2600Ks (since Ivy has no real advantage over Sandy for gaming, the same applies). The FX-8120 is at a pretty nice price point, for some heavily threaded work like video editing, CAD, etc. Its not as good as an i7 for everything, but you can't argue with $160 bucks for an 8 thread processor compared to $300+ for an Intel 8 thread.
Windows 8 is trash in and of itself. I'm not saying you should buy Bulldozer/PileDriver, but buy it for what it can do on Windows7, Windows 8 is just pure garbage for the Desktop market with its "metro" interface.
Directly to the OP in regards to his question,
For your described system usage, I don't see how you need anything more powerful than an FX-4100. I would consider sticking with that until you find something the 4100 isn't capable of doing. None of your described tasks are particularly CPU demanding. I wouldn't crossfire 2 7770s though. A single, stronger video card setup is usually the best solution.