How are you going to manage 172 domains without auto-renew? Unless you only ever buy domains on one date each year, the renewals end up spread out over time, so you have to check and pay every month to keep from losing things.
I'd move to Namecheap right now if
1) They took my American Express card, they only take Visa/MC
To solve 1, if you don't mind using PayPal, you can use an AmEx through them. I know using PayPal brings up a whole extra line of issues, but it does solve the first problem.
172 domains for roughly $1400 @ NameCheap. I had been experimenting with several registrars and they've 'felt' the best so far.