No votes for the GF4 MX ? :lol
My vote goes for the GF4Ti 128MB (any), it's debatable, but IMO they're actually a step up from a Radeon 9600. A bit more raw power. Try to get one with the fastest memory possible because you're sure to be able to run the core real fast anyways (>300). An advice (debatable again), I bought a Ti4200 64MB a few years back because less ram is usually faster ram (check sig).