For me, when I'm getting a new or 2nd-hand GFX card, I will take
a look at the list below and compare the card with others with
similar price tags. I will take it if it's ranked considerably
higher among the cards at its price range.
http://www.overclock.net/graphics-cards-general/270292-graphics-card-ranking-3rd-time-s.html
By the way, the list mixes AGP and PCI-E cards. AGP cards are
getting obsolete and expensive, thus go for PCI-E ones, and take
note of that when choosing a card from the list. Otherwise, you may
head down to SLS asking for a AGP 8800GT and the ah bengs there
will be laughing damn hard at you. Ask the sa jiao queen to go with
you to get more discount as well. 
For the choice of motherboard, if you're overclocking, go for Asus
or Gigabyte. Google for online reviews about them if you're really
into OC. Otherwise, just take up any board that is able to support
your processor and has the features you want, such as a FireWire
port, eSATA support, integrated WiFi etc.
