Look, Graphics cards are hard to guage depending on what your doing.
Are you rendering video's? Do you play and high demanding games that strain the GPU?
My current main graphics card is a EVGA 450 GTS "SuperClock", The 450 is a GREAT middle class card, allows me to render vids, play many games in full graphics.
Its pretty cheap for what it is. In australia I picked it up for about 182AUD but that was from america and it was the superclocked edition so just research around for the normal version.
I wouldnt bother with the 200 series, the 500 series are not really what you need for a medium gpu.
Im going for a 460GTX card when I run 3x Monitors but thats getting abit more pricy.
IMHO, I think either a 450GTS or a 9800GT would be the best suited cards for your needs. You cant really buy 9800GT's new tho.
Im not a ATi person so i cant help you there, all i know is most 5000 series cards are good tho very BIG and expensive
Im not sure If i helped you or confused the hell out of you. If you need any help just ask