My impression of the GFFX line was something like this:
GFFX5800 ~= GF4Ti4600 ~= R9700 (High-end)
GFFX5600 ~= GF4Ti4200 ~= R9500 (Mid-range)
GFFX5200 ~= GF4MX ~= R9000 (Low-end)
Of course that doesn't factor in all the Ultra/Pro permutations. The comparisons are price bracket not performance btw, obviously the R9700 is faster than the Ti4600 but they are high-end cards in their generation.
GFFX5800 ~= GF4Ti4600 ~= R9700 (High-end)
GFFX5600 ~= GF4Ti4200 ~= R9500 (Mid-range)
GFFX5200 ~= GF4MX ~= R9000 (Low-end)
Of course that doesn't factor in all the Ultra/Pro permutations. The comparisons are price bracket not performance btw, obviously the R9700 is faster than the Ti4600 but they are high-end cards in their generation.