Please dont laugh!!

HAHAHAHAHA!!!

Sorry, I mean, what's your budget?

Thanks for your sympathy!!!

I think about £500. Would i hear the benefit by spending more?

your amp is definately the weakest link - I imagine it's really struggling to drive those speakers.  One think, assume your sub is the one that came with your sony DAV unit?  It will be a passive sub.  You'll need an active one to go with a new amp.  I'd look about for a 19** range, a Sony 8** range either discontinued lines (so bargains to be had) and possibly an ex-demo sub from a retailer (Sevenoaks have a large range of these - Subs don't tend to be run-ragged so much). 

That should keep you within your price range.  Take a look on ebay too, you could get some secondhand gems for amps/subs there too. 

EDIT- those are floorstanders?  Perhaps look at a Denon 2310/2311?

And, if you can manage it, try to find (secondhand probably) a centre speaker that matches your front speakers, having a centre from a different manufacturer is going to sound a little odd.

Was the 19** range Denon? and the Sony the 800 or 810 or 820 models?

I see that wharfedale SUB150 has 5 stars would that go with most amps?

Forgot to add, What about Onkyo amps?

Onkyo 509 and a Wharfedale SW150 would be a good shout at the budget. The 609 is a step up, but that's your budget on the amp alone. I've always liked an Onkyo/Mission combo myself. Denon and Mission (well, MX range) is a bit too warm for my tastes.

I would have to agree with most of the above posts, a Wharfdale SW150 active subwoofer is around £150 new or less, get a matching centre speaker to go with you other Mission 702e's off ebay for around £50 or so, leaving approxiamately £300 for an A/V amp. This would include end of lines AV Amps from last years models & a couple of this years, a small list of possibilities to research below for you, all available for £300 or less:-

Denon 2310

Pioneer 920

Onkyo 608 or 509 ( IMO i would go for the 608 if your choice ended between these two)

Yamaha 667 or 767

Sony 820

 Check out Richer Sounds, Sevenoaks, Superfi & others for end of line clearance bargains. This page on What HiFi has a good list of dealers to start off with Clicky

Regards ..

I bought a mission centre speaker  so now all the speakers are Mission.

After playing a few blue rays i must say i think it all sounds really good.

I know that i am using an oid sony surround machine and sony standard speaker cable to power my missions and an old sony woofer but will spending money on a new amp and speaker cable and a new subwoofer really make that much difference?

a new amp will make a huge difference.  your DAV unit was designed to run small speakers, and you've connected floorstanders to it.  Think trying to pull a 40 foot trailer with a rickshaw!  There are bargains out there.  I sold my old Denon 1909 on eBay for £150 last week - look for something similar (although for the size of your speakers I'd look for a more powerful amp - something like http://www.ebay.co.uk/itm/Denon-AVR-2310-7-channel-surround-receiver-ex-cond-/230697527496?pt=UK_AudioTVElectronics_Video_HomeCinemaSystems&hash=item35b6a4e8c8 (although I'm not vouching for the vendor).

You'll definitely hear an improvement with a better AV receiver & subwoofer. I can't comment on speaker cables as I have no personal experience.

I agree the gains with something like this 2310 will be massive.

I'd be inclined to get an amp, and do without a sub (run as 5. until you're able to spend another 200 or so (as your Sony sub (being passive) won't work with an AV amp).  Speaker cables - get some £1 a metre copper ones from Richer Sounds.  Perhaps Cambridge Symphony 200 for fronts, and Cambridge Symphony 100 for rears.

stupid emoticons - 5.0.

Good advice given above. Change the amp first, followed by the Sub (check out BK). Finally use a good copper cable like Chord Carnival Silver Screen or Wireworld Stream 16/2