Cheap Catalytic Converters
 

I need to replace the rusty exhaust on my late 2000 100k 986. Given the mileage I'm thinking to replace the cats too if I can for sensible money. There are lots on ebay priced between 75 - 160 UKP (nearsides seem to be 30-40% more expensive than offsides - a bit odd.) Does anyone have any experience of these? None specify they are stainless steel, should I therefore presume they are mild?
Some suppliers list the same cats as being for all 99 - 04 models, others separate 07/99 - 02/01 from later years. Is type approval the only difference IE does one size fit all or do the early ones have only one O2 sensor and the later two? Legally I don't need type approval but is it worth paying the extra thirty quid a side or so to get it anyway?