I've only used Mazda Parts mainly, I have got HME seals in my series 5 N/A though, mainly because I didn't like the 3 piece seal
price 
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A PP is not a good choice for the street due to the power band (it's up way too high) and this range is high wear too. You will not get 50K from any PP unless you drive it out of it's power range all the time. A std 12A will last 200k + if it's driven like a taxi, if you constantly drive in the power band of a PP this is about 3 times higher wear alone, add the bigger clearances and you can see where it's going....
Anyway, For a PP I would say a 1 piece seal of Carbon would be my choice. They were used for years in US endurance races without failure. When they chip/crack they don't always cause the damage that the std cast irons ones do either.
Also, if you are going to have a PP make sure you fit a decent EFI set-up, a carby is no good. The inability of the carby to cover the rpm range of this type of rotary leads to slightly leaner mixtures at high rpm. You have to run bigger clearances to accomodate and this means hard starting when the engine is hot from seal leakage.
There are currently Bridgeport engines in IPRA that are more/less a PP in their HP/rpm range anyway, best to talk to Ric Shaw, Bill Nabham, Rohan Ambrose or one of those types of engine builder, not a forum junkie. If it's a turbo then talk to Pete Basmadjn from Simply Maz (I know he sold the business).
Like Graham Russell, most established gurus spend little time on internet forums.
Cheers
Daniel