I must be honest I wouldnt be keen on a 2nd hand card either....I have always found that they have a certain life span and if you getting a 2year old card, well you may only have a few more months left in it before it gives up the ghost.
All components have a lifespan but it depends mostly on how badly it's been treated and even then they can last ages (excluding faults, power surges etc...) . I've still got a Geforce 4 Ti and even a 3Dfx Banshee in perfect working order despite the Banshee having been overclocked by more than 100%, so much that the board was burnt to a brownish tint in certain places and still works to this day.
If it's been working for two years it shouldn't suddenly die from normal use, infact it's more of a testament that it doesn't have any faulty parts.
Even so I would stay away from things like second hand hard drives as you can't quickly plug it in to see if it works to be sure nothing's wrong.
things the HIS HD4670 iceQ turbo has over a 9600gt is:
very good cooling
slightly cheaper then the cheapest 9600gt
factory clocked
ati stream (free encoders lol)
reliable, seems like the ati cards are a little more trust worthy then the nvidia atm
it's got a decent amount of room for overclocking