Hey,

Have you ever considered using AGG as the rendering engine in Inkscape?
AGG (AntiGrain Geometry, http://www.antigrain.com/) is a very high quality
and fast C++ 2D graphics engine and there's even an SVG renderer based on it
(http://www.antigrain.com/svg/index.html).

Cairo seems to be very slow in all the benchmarks so I don't think it's very
suitable. You should take a look at the AGG examples and join the AGG mailing
list for more info.

 -- Juha Varkki