John/Jules
A lot of the manufacturers are advising against playing the discs in their machines. If you do order from the US site be wary of customs charges if you order in bulk to save on postage.
If you want some "dual discs" why not got for the hybrid SACD discs? If (when?) Sony do drop SACD at least you will still be able to play the CD layer. Also every DVD-A disc will have a DVD-V Dolby Digital layer and sometimes a DTS track too
Buy these and get the most out of your fabulous Denon NOW

Try Amazon.co.uk or Play.com and you'll get a great selection of both DVD-A and SACD hybrids for between £8.99-£15.99.
I've got nearly 100 SACDs and DVD-As and I've not had any problems at all. I just sit back and enjoy