Ooo lots of questions

I'm talking from a Mac perspective, your mileage may vary (and almost certainly will, if my experience of Vista is anything to go by)
1-Does the Airport connect via your existing router, or does it connect directly to the PC you are streaming music from? I have a PC which is connected to my current router via ethernet cable rather than wireless, so I'm wondering if this would pose a problem? Apologies if this is a daft question, but it's late and I've been on too many Mac forums!
Either, though if you want the AE to be wireless, your router will need to be wireless as well, obviously. Once it's set up, it will just be 'on the network', and anything else 'on the network' will be able to see it.
2-Can the AirPort receive music from various PC's, or just the one? I also have a (Windows) laptop connected to my router wirelessly.
See above.
3-Are there any official ways to control the system remotely? Or would I need something like Salling Clicker?
Official as in Apple - no. You can get (cheap) software for the (expensive) iPhone or iPod Touch to do it.
4-If I was planning to add several AirPort Express, in various rooms, would it be beneficial to replace my existing router with an Airport Extreme?
tbh, I'm not sure where the 'n' wireless standard is going, as it's not agreed yet, so you
may need an actual airport extreme base station to get an airport express-compatible 'n' speed network. Theoretically though, any 'n' speed router
ought to work. I only have 'g' so can't comment.
Or would it be simpler to avoid Apple altogether and go the Squeezebox route?!
Well it is more flexible, certainly, and for the incremental cost (by the time you add a DAC and work out remote control), you might find it a better idea - I would suspect that it sounds better than a cooking Airport Express, since as you may have seen in an earlier thread, its default sound quality is noticeably inferior to a good CD player, even with lossless - despite initial very favourable impressions with classical, with voices it's a bit woolly. I am looking to augment it with a DAC soonest (and now think I might have been better off with a Squeezebox in the first place).
5-Are there any other DAC's I should be considering other that the Beresford (ie cheap!)
There are a few on eBay which I like the look of, but all from China and of indeterminate quality, other than from feedback. At least the Beresford has positive real user reviews here. Am considering a Moodlab Concept, but even that's a bit dear.
But instead it just kept on raining
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