You will also need a cigarette lighter socket in your car and a power cable to link up to the PDA holder. The holder will power up your GPS device.
I have the rz1710 too and it has been very reliable. Make sure you get a bona fide version of TomTom (the best navigation software in my opinion) - you will need an original product activation code (comes with the software) for it to work.
I would recommend obtaining an SD card too - 512MB or 1GB and copy the TomTom files over so that you can hold downloadable POIs such as shops, speed cameras etc (see
www.POIedit.com). Keep the original SD card though! 1GB Kingston SD cards are about £16.00 now on eBay...
Have a look at Mio 168 too, or perhaps the P350 - both have in-built GPS receivers. However, AVOID the P550 for now - I've just sent one back as it didn't work properly!
Best wishes
Gavwad