OK - I am upgrading the following. Yamaha DSP-A5 onto Bose AM series I front and sub, Eltax Bipolar rears and Centre. Step 1 - The amp needs a facelift. On E-Bay I am looking at a Denon AV-3803, how much money is too much?, I am also looking at a Yamaha RX-2400RDS, same question - how much? Are these decent choices? - I like the 2400 because it has THX certification and is a bit more future proof but I am impressed by the reviews I see of the Denon. Are there any others I should look for?. Step 2 - Speakers. I am not sure the Bose handles the soundstage that well given the way in which it insists on managing my fronts and not using my sub output so I'm tempted to upgrade the speakers too - but to what ? - there is so much choice. I'm happy to go secondhand so if I were to say the budget is around £500 what would you look for.