What Registrar to use?
 

to manage a large volume of domain names?

I use namecheap and Godaddy (non adult) , never been fucked about with those

i always do our bulk purchases with godaddy, no problems at all

I dont know about namecheap, but fuck godaddy!

http://natnames.com/ <-- Not the cheapest, but nice to work with...

Dotster.com

http://www.directnic.com

ICANN approved, owned and run by guys who started in the adult biz, the best I've ever dealt with, and they have volume discounts! I don't want to put words in their mouth, but I bet they'd be willing to work out a discount for you with a large amount of domains :)