AV Speaker upgrade puzzle

Hi Everyone

Looking for some help with a bit of an upgrade quandary.  My current system is:

Roksan Caspian Integrated Amp

Roksan Caspian 5 channel power Amp

Yamaha DSP-E800 surround processor

Squeezebox touch and M2Tech Young DAC

It’s the speakers that are causing me think….I currently have:

KEF Q35 (1990s) as my main speakers – and they are bi-amped. My rears and centres are some old Gale speakers purchased as a cheap experiment in to 5 channel AV about 10 years ago.  I also have a Yamaha sub  (purchased when I got the Gales).  The sub is due an upgrade and I listened to a friends BK Electronics XXLS400 which impressed me.  My system is mainly used for music (about 70%) but movie via bluray is getting more frequent.

Here is my quandary – I am quite happy with my KEF Q35’s as my main speaker, but I realise they are old and I could probably do a lot better – and would probably take a look at changing them in the next 2-3 years. 

It’s the centre and rears that need changing but what to get?  Do I just get some “cheapie” (ex-dem or old model) KEF rears and centre to match my KEF Q35s?  If so what ones to choose?  Would an iQ60c centre be ok?  Or do I get some more current and expensive KEFs for the rears and centres, but lock myself into a KEF upgrade path for the fronts? 

Or the big question – do I look at the complete system now and go for one of the AV speaker packages – I am quite taken with the Monitor Audio RX silver package.  If I am replacing the whole lot now then I guess my budget would be about £2.5k

Thanks for any help you can offer

S