Class 5 Environment

I have heard from several carriers I work with that they are testing Asterisk servers for use in a class 5 environment. I even know of a few who have deployed them.

We have pieced together our VoIP network with seperate Media Gateways, and SBC’s instead of going with a full Class 5 switch like a MetaSwitch or CopperComm.

We wanted to start testing an Asterisk server for use as a Class 4 (or Class 5 if possible) switch and from what I read on the forums it seems like a beefed up system is the key.

I was hoping to hear from someone who knows the best route to go, in an environment that would start out with about 500 concorent sessions (SIP to SIP, H.323 to SIP, or SIP to TDM) and be expandable from there.

What hardware do you suggest?
Is there any cards that can support a DS3?
From what I read, the Asterisk dosen’t have a native support for SS7, but has anyone gotten a SS7 link to work?
Has anyone used one inside a Class 4/5 environment?