I upgraded to the Denon AVR-2311 two-and-a-half years ago. I have so far continued using the speakers from my old system comprising of the Technics SB-A37 front speakers (floor standing) and the Technics SB-CSS70 centre and surround speakers. Unfortunately my Technics SB-W33 sub-woofer is not 'powered' and could not be used with the Denon 2311. Although the speakers are in good condition, I am considering upgrading the speakers package. The dealer advices me to continue using the Technics SB-A37 front speakers and change only the rest. Any recommendations? Also, besides age, what else makes these speakers outdated or incompatible with the modern AVRs?