Actually the 2007 Mio range (C220 & C520) were the first in the Australian market to be released with the v14 sensis maps. Depending on how much you want to spend both are great at what they do.

The Navmans aren't worth looking at at the moment. Mio actually bought them out at the start of the year so I would say their future models will be better.

The C520 has the option for TMC which will be coming out in Australia very soon also. Real-time traffic info sent to your GPS to avoid congestion and accidents etc. Cool stuff.