At this level I'd say minimize the cost on the receiver and put more of the dough in the speakers. Just make sure you get the features you need. I don't think preamp outs are necessary -- chances are if you're going to add higher quality amplification you'll want to add a better prepro to go with it. And I'd recommend getting a model with some kind of digital sound correction since you've mentioned you may eventually go to a 5.1 setup. I noticed you could get the Pioneer VSX822 from B&H Photo for $272, and that should get you everything you need or the 1022 for $299 if you want things like video upscaling, component video input, etc. Onkyo TX-NR414 also looks very good for $295 and may have more inputs if that's a concern. Any of these receivers will probably be fine, but speakers are a tougher and more important question at this price level imho.
Buying used can be great but also very hit or miss, and finding front L/R/C used can be tough (although the Def Techs Realremo found could be good). Another route would be to look at something like Hsu Research Value 2 package (3.1 setup) that you could get for $800 -- good value since you buy direct from manufacturer and avoid dealer markup, and you can add matching surrounds later as budget permits (and you get a warranty too). Short of that I'd look for a good pair of used monitors and a sub and try to find a matching center when it becomes available. If the monitors are decent quality and set up well you may not miss the center channel too much for a while. I think Paradigm (Monitor series Center 1 for example) and B&W (used Matrix HTM with single mid and top-mounted tweeter) make some pretty good center channel speakers so they might be a couple brands to look at for monitors as well. Since 85% of your listening will be for movies/TV I'd try to get the best center speaker I could since 80% of what you hear will be coming from it, and there's nothing worse than listening to voices in particular through a crummy center speaker (probably better to use no center in that case).
If cables/interconnects aren't in the budget you can get by with some from Monoprice (definitely for HTMI cable) until you can affort to upgrade. Again, I'd put as much money as possible toward the speakers since they'll make the biggest difference on an absolute basis at this level (assuming you don't use a garbage receiver or cables). Hope this helps and best of luck.
