There's so many options open to you that it could take the best part of a page to document them, so I'll follow 2 likely scenarios...
1. You play PS3, DVDs, TV more than you listen to music.
In this case, I would recommend a good AV amp/receiver with a dedicated 5.1 sub/sat setup. If £500 is at the top of your budget (and you don't want an all-in-one brand package), then I think you're on the right lines with the Cambridge Audio 540R at £270. It's probably the most 'musical' sounding AV amp around that price, but also consider the Sony STR-DA1200ES which has had all the good reviews and can be picked up for around £330 if you shop around. I have the Sony and it outperforms my previous Yamaha DSP-AX750SE (RRP £500).
Speaker-wise, you'll be struggling to get 5 speakers and a sub for £250 that will do any justice to music. If you like the sound of the Wharfedales, then perhaps it's worth just getting the front two speakers and sub then adding the surrounds when funds allow? A rival to the Wharfedale 9.1 package would be the Quad L-ITEs retailing for similar money, and very popular on these forums.
2. You listen to music more than watch DVDs, play PS3, etc.
With a budget of £500, you can't beat a stereo integrated amp and a pair of half decent speakers if sound quality is your priority. AV amps are built to handle at least 6 speakers and all manner of inputs and processing, so it's no surprise that a similar priced 2 channel amp will comfortable outperform a home cinema one. I'd be looking at Cambridge Audio again, perhaps a 540A (version 2), Rotel RA-05, or Rega Brio 3 with either the Monitor Audio BR2 stand mounts or Bowers & Wilkins new 685 or 686 speakers. Both Monitor Audio and B&W have sub and surround options you can add later.
This is the route I took - first having a good stereo setup, then adding an AV amp to handle DD/DTS and power the centre channel, sub and surrounds.
There's a strong second hand market for both these options, particularly with the amplifier part of the equation. The AV scene moves very quickly and you can pick up discontinued ex-award winners in the 'mid' price range at budget prices very easily.
Hope this helps, and good luck!
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