Ask YC: Good SIP termination/trunking provider?

I'm in the very early phase of doing a VOIP startup and I was wondering if any of you know of a good VOIP service provider that offers connections to and from the PSTN? I have checked out Teliax and Bandwidth.com SIP trunking.

We're planning on handling several calls at a time, but each call shouldn't last for more than a couple minutes.

Also, does anyone have a recommendation for a data center that can easily handle steady traffic that would tend to flow through an Asterisk box? We're looking at The Planet right now and haven't found many other suitable options.

Thanks!