The latest and greatest would be the V3001 series ( make sure to get extended memory ) . I believe that the product would still be available via the vendors as we sold our last ones back in October . Also , I'm sure that either HP or your vendor could help you with a contract for a few years if necessary .
The NBX 100 only had 100 devices ( tels PRI channels etc ) .
The V3001 will have 250 devices to start with and the 6.0/6.5 license already on the box I believe when you buy new .
Also the extra memory is a good thing to have versus the number of devices . You cna use the old NBX 100 Chassis for your PRI and Analog cards by purchasing a hub card to plug into it . Now you have a remote chassis that will connect to the new V3001 system . No need to purchase a new chassis . Just remember that you may have to purchase licenses if you have any 3100 series tels , and maybe tels if they are the 1100 series tels as they are not supported anymore on the newer platforms .