its a good idea, but very expensive. ps3 heatspreaders are about 4cm x 4cm for cpu, and rsx is a bit bigger 4,25cm x 4,25cm. PTM pads are cheaper.
ptm and carbon pads, they will last longer and will not pump out compared to thermal paste. Carbon pads will not dry out compared to PTM.
its a good long term investment if consider carbon pads.