First thing, it's a Core i7 860, not an i5. However, it uses a Socket 1156.
The alternative is Socket 1366 based system which will work with Core i7 9xx processors and next year's Core i9.
The Core i9 is a 6 core processor (see http://en.wikipedia.org/wiki/Intel_Core_i9) with up to 12 threads. For the applications that you listed, it is probably overkill, but some people would want to be able to run one just to say they have one.
You also mentioned that saving was important to you. The Socket 1156 processors are rated at 95W whereas the Socket 1366 processors are rated at 130W. So if you want to keep your electric bill low, you should stick the Socket 1156 line.
As for concrete recommendation, since your purchase date is so far out, it's hard to recommend specific things since specials and discounts come and go.
Agree, Christmas '09 is still a good 3 months away. No one was expecting the i5 to out perform the top Phenom II 3 months ago. Heck, the majority of the recommended gaming builds were Phenom II a few weeks back. Who knows what will happen between now and Christmas.
I believe that you can get a decent i7 920 Socket 1366 build with your budget, but the 1156 i7 or the i5 will serve your purpose as well. I wouldn't go for the Socket 755 based Q9550, though, since you'll have to get a new Mobo, CPU, and RAM (maybe even the CPU cooler) if you are to upgrade your system in, say, 2 years.
Going for power saving can be tricky; easy to be penny-wise and pound-foolish. If you have an older PSU though, particularly one with a little red voltage switch on it, upgrading that to one that is 80+ certified will not only save power, it will also be better for the longevity of your parts.
If you just have the urge to build because it's a hobby and something you like to do, then build a second machine for everything but gaming and high-end graphics applications. Put a 45W AMD 4850e (or similar) on it, with either the IGP of a 790GX or 785G mobo, or with something minimal like a HD4670 on it. Use one of the little (300W-350W) Seasonic 80+ bronze PSUs to power it. Then only turn on the primary machine for games, and do everything else on this juice-sipper.