I realised that Windows Mobile Device Center 6.0 and 6.1 weren't in the DLC and have uploaded 6.1 and 6.0 x86, but I don't have the 64-bit AMD64/x64 .exe for WMDC 6.0.
Has anyone got it lurking anywhere from the annals of time?
Archive completeness. Every other version of H/PC Explorer, CE Services and ActiveSync can be downloaded from here. May as well have a full house.
The softonic link is offering the x86 installer file (and a bucket load of malware and spyware traps) and it actually just hotlinking it straight off of download.microsoft.com. So we can conclude that the x64 version is too. I just don't know where as you can't deduce the download.microsoft.com URI from the www.microsoft.com/downloads/ URI or source code.