asterisk users - Feb 2013 - Recommendations for SIP to ISDN PRI E1 gateway to use with Asterisk?

Hi,

Anyone who has experience with ISDN PRI voice gateways?

My customer wants to connect some E1 equipment to a gateway that 
converts from ISDN PRI E1 to SIP/RTP. The data will be transmitted over 
a WAN, and into an Asterisk-1.8 server.

It's one E1 on each site at 8 sites, and they are asking for our 
recommendations on gateways.

Your advice on this topic is very appreciated!


-- 
Johan Wilfer