Two Channel: Totally content with system. In all honesty, my speakers/sub are more than I have the right to ask for in a roughly 28 foot by 18 (partly 24) foot room, domestic setting. Many pros wish they could afford this kind of setup for daily use at work. Fortunately, I don't need a console and a bunch of other costly mix gear for playback - so I can afford to put the bulk of the investment into the speakers and room setup.
I plan to make some further room acoustic treatments to treat long reverberation times in the sub 300 Hz range and then I'm completely done for two channel....yup I can die happy!
I plan eventually go full 5.1, and I seriously doubt I'll go further than that (6 or 7.1).
5.1: Currently missing a center channel. Philosophy is same as two channel: must be high quality timbre matched speakers (otherwise I see no point in 5.1 at all, after all, who wants cheap sound from five directions, I'd rather have the best sound I can afford from two directions first, then work up from there!). Since my 36" HD TV is CRT, I'll have to replace that first and install LCD/plasma before putting more than 22 pounds of driver magnets anywhere near it.... a rather big and costly step, which will take time, as there is no urgency.