What are you planning on doing with your PBX? A hosted Asterisk solution is going to be limited in alot of respects: # of concurrent calls that it will handle, call quality, etc. This is mainly do to that fact that you really don't know how the provider is setting things up. If it's a VPS setup, how many other VPS's are setup on the same node? If it's extension based virtualization then you still don't know how many other "hosted" users are on the system, and what their call volume is. If there's alot of IVR or audio playback, it can require a heavy amount of CPU if not encoded in the proper codec.
I would always suggest putting together your own Asterisk box. That's going to give you the best quality. Plus you'll be in control ;-)
If you're worried about finding a good VOIP carrier, that's plenty out there. A few:
Junction Networks - Been with them for years. Fairly solid, and provide support via email and phone.
Bandwidth.com - Great connections. They are the largest reseller for Level3 Voice termination.
Vitelity.com - They are been pretty good thus far. I have only been using them for a few months.
Well only person we have seen offer that price for pbx would be *********** they run our phone system we only pay $23.99 but on there site the price is different your best bet is to contact them. And if that doesn't help phonepower.com is decent too but a little more expensive