a few points: AGP is old tech... PCIe is the latest
if you want to get this done as quick as possible and budget isn't a huge a concern for you? (& I get the impression you are not a big gamer, and not playing the latest bleeding edge games) then why not just rock up to one of the reputable stores in auckland that meesham suggested and buy what they recommend. You can bring along your computer to make sure you get the right one, and if you are the nice they might even install the card for you right there in the store ;)
might cost you an extra $30 or whatever because you haven't picked out the most *perfect* value card for your purposes but you'd get it done right now without any extra hassle or research :)
not what I'd do however... but that is because I like wasting time reading up reviews & on forums ;-P
edit: oops, only just now read through the whole thread...