#1 and #2 can be done by pretty much any decent AV receiver, and you could add a set of wireless speakers to cover #3. Though wireless speakers mostly suck unless you spend a LOT of money on them - I've been looking for a wireless set to use as surround speakers for years, and there aren't many options that seem to have a decent reputation. Can't you just use an adapter to cover #4, rather than having to buy a system specifically made for it? AFAIK, since it takes a good deal of power to run speakers, most systems are optimized for one voltage only.
You can probably get something decent for under $500 by buying the parts separately (though the wireless speaker part may be hard, as mentioned above). A solid receiver from Onkyo, Yamaha, Sony, Denon etc. will run you around $200 to $300, then you have to find speakers, but I don't know what wireless speakers cost.
Spend some time searching reviews at CNET, there's a lot of info there.
Outlive the bastards - Ed Abbey
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