First of all I'll confess I'm no expert at this.
You can certainly get wireless speaker systems, but they are usually sold in pairs only, for example as rear speakers. I didn't think the Gigaworks S750 was wireless.
There are some 5.1 wireless speaker systems around, for example Jazz J9940W, but beware because often the front speakers are not truly wireless but instead plug into the subwoofer, which itself is wired. This may be OK for you though.
For the projector, you can buy a wireless adapter to convert it, but they are expensive. Alternatively, the Toshiba TLP-T520 is wireless.