Well, this is going to sound strange considering the state of things, but I have to reccomend a ATI 9600 Pro.
I know -- it has directx9 capability, but many see it as lacking the power to match. That's normally the order of things -- if there's a midrange or budget newer card, with "support" for a lot of new features, that generally means that it's the worst of both worlds -- a card that can run advanced features at 3 fps, without the power to provide topend performance in earlier games.
But this latest HL2 debacle, and the ensuing sets of benchmarks, we're starting to see a shift! It turns out that we are FINALLY seeing GPU-bound games now -- that hardware is almost never fill-rate or bandwidth-limited. Most existing cards can handle and use about as much geometry and textures and even bump maps as even the most next-gen of next-gen games will be throwing at them for quite some time -- because as we go forward, the limiters won't be storage. It will be procedural ability -- how the graphics card can use the same textures and bump maps and geometry, but light it better or more realistically, or apply cooler new effects, render better particles/hair, etc.
What does this mean for us?
This means that once our card is fast enough to run ut2k3 really well, we need to start looking at its shader capabilities. And the fact is, this latest HL2 debacle has shown that nVIdia's cards are fuding a lot of their DX9 capability -- relying on fill rate and bandwidth (although they barely have a lead there even at the high end), while skimping on registers for shader execution at high precision.
Look at the Half-Life 2 movies. There is a clue for the future of games -- the actual geometry in the rooftop scene is, complexity-wise, almost put to shame by UT2k3 and Quake 3 and so forth. The bumps and specularity maps aren't particularly high-rez. But because they're using High-Dynamic-Range lighting, they avoid the banding effects that can impede the realism of a lot of pixel-shader implementations, as well as handling 'glare' lighting a lot more realistically. The overall effect is EXREMELY realistic environmental lighting, on a lowered resolution, but of the same type the we are used to in professional rendering packages for special effects and the like.
And that shit runs on a 9600 Pro playably.
I would totally go with a 9600 Pro right now. In fact, I am -- I lost my nVidia 4200 128mb a while back to an accident, and the 9600 Pro is almost certainly going to be my replacement.