I would have to say that ccbill.com is the best out of all of them, no setup fee, (subscriptions) member management, checks sent out on time each month, there just a great company, However, I do use worldpay.com, but they do have a high volume start up fee. Best thing to do is check them all out, and decide which one you pefer after you know all the facts about each and every company.
you will need to check out all there websites to see there prices, I would also do background research on paypal before you think about signing up with them cause i dont know about anyone else out there but they certainly screwed me over backwards.
the thirdparty processor i use are:
NOCHEX - with a processing fee of only £0.99p no matter how much you transfer.
Fastpay - Havnt transfered money using that, but i got an e-mail about them thinking about it being free.
I have not had any trouble using any of these processors and would recomend them.