When it is time to upgrade, how long from today? How much do you think your budget will be? How big will your new space be? These are sure unknowns. So here are my suggestions:
Get a good sub, one you won't have to upgrade when you move to a bigger system. You'll find good ones at sub$600, look into a popular line so if you want/need to, you can add a second sub of the same model later one. In other words, a one time investment.
For speakers, I can only speak for the Pioneer BS22. For less than $100, you get a good pair of speakers. They are well balanced, affordable and easily upgradable a 5.1 setup if you get a couple hundreds to spare in the near future. They are widely and highly praised, so you won't feel bad you spend so little or got something cheap. Having them toed in a little and in a calibrated system, I get good "phantom center" when I have tried it (although i do the center speaker, but i wanted to try it nonetheless). Imaging is good for the most part, sound stage is a little narrow, but not bad. All in all, It is a good sounding starter set of bookshelves, allegedly unmatched at this price point.
For the receiver, just get a mid powered 5.1 system, with the features you need. With Dolby set to release a Dolby Atmos home theater solution in the next 2 or 3 years, and probably DTS following suit, you may need to upgrade your receiver later.
Just my 2 cents.
Yamaha RX-V673 | HSU HC-1 MK2 | HSU HB-1 MK2 - LR | Pioneer SP-BS22-SLR | BIC RtR-V44-2 (Presence)