Generally, it is most cost effective to save your money and buy speakers that you never feel the need to upgrade. Speakers don't need to be changed when they come out with some new format or feature, so they tend to be useful for a very long time. Most people, however, seem impatient and so they often go through many sets of speakers (and other gear), which costs more money in the long run.
Since you will soon move to a house, I recommend that you wait at least until you move before buying anything. Anything you buy now you will need to move, and that is more trouble and runs the risk of damage during the move.
I recommend that you go to all of the audio stores in your area, and listen to all of the speakers that are within your price range. With speakers, more money often does buy better sound, and so you may want to consider whether it would be a good idea to save up for some really good speakers, or keep things within your current budget. You might also want to consider just buying a pair of good speakers with your entire budget, and get the rest later when you have more money. The risk with doing that is that it may be that you will have trouble matching them later on, so some people like to get the front three all at once to ensure that they will be voice matched.
For subwoofers, I like SVS, though there are other brands that are also good. But I think SVS would cost you more than you seem to want to spend:
High Performance - Subwoofers - Home Theater - SVS
I recommend not getting a cheap subwoofer at all, and save up enough to buy at least their bottom of the line model.
On a very tight budget, I would go with just a pair of speakers, buying the best that I could afford, instead of getting a bunch of lesser speakers. I personally value the quality of the sound more than I value having sound coming at me from all directions. And although I really like deep bass (I have 2 of the old SVS CS-Ultra subwoofers in my home theater), I would rather give up some deep bass than to have the rest of the frequencies not reproduced very well. So I recommend getting a pair of speakers that you think are good enough to never need upgrading, keeping in mind that eventually, you will probably add a subwoofer, so the speakers selected need not go terribly deep. If they are good down to 60 Hz, you should be fine for blending with a subwoofer later on to get the deep bass, when you have the money for it.