I won't steal Mike's thunder, but as ever it depends on what you need.
Big display (but Garmin memory cards) - 276
Small, internal battery - Quest
Sophisticated driving (no battery, more expensive) - 2610.
I bought my 2610 in the US - I actually used Amazon.com and had it shipped to someone in the US, then collected it when I went over. Amazon had a good price and was the only US merchant that would ship in the US on a foreign credit card. Worth checking out.
I now regularly use the 2610 here in the UK, but I already had a European City Navigator from an SPIII. The unit you buy in the US wil have a US basemap - NOT a Pacific one, so if you're planning on using the unit in NZ, you'll be out of luck. I know there's an Australian version of City Navigator, but I'm pretty sure it doesn't cover NZ. If you just want to use it in the US and then sell it, you should be OK.