Personally I don't think the two S's joining the 2nd and 3rd words together is all that smooth.
If I was registering something like that my preference would be
JoesBlogSpeaking
or
JoesBlogSpeaks
as for extension either .com or .com.au
my theory is... if targeting global audience go for .com (and maybe not worry about .com.au)
If more aimed at Australia, and you want a bit of google geotargeting even if you are hosting the domain overseas, then make .com.au the main domain (but grab the .com anyway if available)