I think 5-10 deseeded and deveined habanero peppers will be plenty of heat. The habanero itself has great flavor I do not like the flavor of the seeds or veins. But, again, it's personal preference. I prefer the pepper flavor over the heat. But if you want heat I'd ssay add more de-veined/de-seeded peppers, don't add the seeds. That way you will get more of the fruity character from the pepper not just be heat centered beer.