"Zones" are exactly that - different zones of independent audio and/or video, as in different rooms (they don't have to be bound to a room though); your processor generally determines how many zones you can have (however this isn't concrete).
As far as the speakers, impedance ("ohm wise") doesn't matter for matching unless the amplifier chokes with things mixed (shouldn't), so do whatever suits your space and taste. Grab a receiver with multi-channel preouts and multi-zone (if you want it or need it), hook the amplifiers up for the appropriate channels (I'm not sure that they're better than "any under $2000 receiver", but I also don't know how much power they're supposed to be putting out (And how much yours will actually put out, after however many years of age)). An example of a suitable receiver here that should also be sold at Best Buy (so you can go and look at it) would be the Yamaha RX-V867, the RX-A700 is very similar but I'm not sure if Best Buy sells that model. There are also models from Onkyo, Denon, and Pioneer in that rough price range that will offer pre-outs. Sony doesn't offer anything in their non-ES catalog currently that has pre-outs (which is a real shame), but if you're interested you'd need the STR-DA3600ES (or higher), which Magnolia should have (along with some nicer Denon models).
Basically you'll be dumping all of the EQs, meters, preamps, etc (I don't care or want to know what you've done with them - sell them, recycle them, etc; if you decide to dump them in a field or put them in the trash then you shouldn'tve had them in the first place) - the AVR will handle all of that internally (and probably better/easier) - keep the power amps, speakers, and subs, and all should be good. You can probably hook up at least two, if not all three, with a modern AVR (depending on how they're able to be connected this may be incredibly simple).
Regarding 7.whatevernumber, it doesn't exist - it's 7.1 with multiple subwoofers (they aren't drawing from discrete channels and generally draw the same signal or very nearly the same signal (some AVRs/preamps will "split" their bass management for stereo, so all left channels go to "left sub" and the same for right, but LFE is still sent to both as if it were one)), and in general 7.1 itself doesn't exist (almost all content is 5.1 and upmixed/remixed to 7.1 by the receiver) - so if you don't have the space or budget for 7.1, ignore it (it isn't "bad" but you won't be missing anything with the vast majority of content, especially from DVD and cable/satellite - once you go over 7.1 however, it can get somewhat "nuts" (9.1, 10.1, 11.1, and so on are generally proprietary to the respective equipment manufacturer, with the exception of Pro Logic IIz and Audessy DSX (which still represent remix/upmix schemes, not content encoding)). With a pair of quality stereo power amplifiers I'd probably consider 4.x (if your space is small enough), or 5.x if you really want the center channel (or your space is larger), 6.x/7.x if you have the equipment and space (some newer Blu-ray titles are 7.1, and there's some 6.1 content on DVD and Laserdisc that can be played back on 7.1 arrays, your PC can also output 7.1 from games if it has proper hardware and your receiver accepts 7.1 analog multi-ch input). The reason the subwoofer thing matters is that you can go ahead and connect all three if everything allows it (again, it depends on how the subwoofers are able to be wired in), it may or may not be "good" in your space (you may have artificially inflated bass response centered on a given frequency, or you may just waste a ton of power and gain nothing). Some fancier receivers labeled as 7.2/9.2/11.2 will do bass management independently on their sub preouts, which is a nice feature (it helps integrate multiple subwoofers more easily), so keep an eye out as you review user's manuals and spec sheets.