AV receiver for use as a pre-amp. Buy a new one, ex demo or second hand?

I'm after a AV receiver that can decode the HD audio formats and has at least 5.1 pre-outs and has a GUI that is output over HDMI.  I would also like 2 HDMI outputs but that is not mandatory. I would prefer another processor but I don't think there are any within budget.

I'm mainly interested in sound quality.  I don't care if the amp has all the network functionality, ipod connection, multi zone, wireless, waffle iron etc.

Would I be better off getting a new/newer AV receiver if the decoding of the HD audio formats are better than those of older receivers? Or will I get more for my money buying an ex-demo or second hand receiver? I would like to have some warranty.

I have not auditioned any but the general consensus is that the audio quality of Yamaha is generally very good.  So I have looked at old Yamahas like the 667,767,3900 and newer ones like the 771,810. 

My budget is around £500 but this can stretch a bit.

I would continue to use my old processor for the non HD formats.

I currently have a Primare SP31.7 processor, Cyrus MonoX amplifiers for the front 3 speakers and a Cyrus linkpower for the rears.  My speakers are all Dynaudio.  The fronts are Confidence 1.8mk2, Audience center 122, 42w for the rears.  The sub is a Sub500. 

I'm not a fan of Onkyo but any other recommendations are welcome.

Thanks

Hello!

Assuming your source is a BDP, have you thought about using a six-/eight-channel analogue connection to your processor? There are several players available within your budget (e.g. the Philips 9600, Cambridge Audio 651 or Denon 2012 if you shop around), if yours isn't sufficiently equipped. Might be more comfortable to handle and take up less room than another AVR (and certain to consume less power).

I did consider that but I have a PS3 that I would like to use with the HD codecs and I am currently building a home media server which outputs audio over hdmi.

You have a brilliant processor, you're not going to get close to its quality with £500. I suggest either getting a BDP with multi channel outs (as suggested) or getting the HD audio upgrade board for the primare. 

The Primare I have does not support the HD board so I was looking for a stop gap solution to provide HD format support until I can afford a better processor. I know a £500 AV receiver is not going to be as good as my Primare is but for now I just want something 'decent' to provide HD audio support.