Seeking advice on a new video card

[cmdr_zoom]

So I've decided to be a little more discriminating than just "grab whatever I can find fast and cheap and slap it in," and take the chance to pick out something that (I hope) will last me a bit longer. Something in last year's model, not four or five years ago like I have now (and not this year's or next - that way lies madness and $500 price tags for something that's going to get a price cut and die shrink right about the time I take it out of the box).

I'm something of an ATI loyalist despite their spotty support for one of my main games, City of Heroes, mostly out of a combination of laziness (I don't want to research a whole 'nother product line, or go through a full driver scrubdown and reinstall; it's been "good enough" so far, so why change?) and sentiment (probably misplaced and/or irrational). And they do seem to have gotten their act together lately with regard to OGL support ("I tol' you, he's changed!"). But if you have a compelling argument for switching to nVidia, I'm willing to listen.

My budget or price-point is in the area of $50-$100. My bus is PCI-e, my power supply is 400W. I'm presently leaning toward something in an HD 46?0 or a 48?0, or possibly a 36?0 or 38?0. Please feel free to tell me why these are horrible cards and plunge me back into a paralyzing morass of doubt and worry.