i have a 5639 dualsocket server , running ubuntu 12.04 amd64 primecoin-hp10 
and here are my results :
primecoind getmininginfo{
    "blocks" : 138481,
    "chainspermin" : 46,
    "chainsperday" : 3.77730295,
    "currentblocksize" : 1000,
    "currentblocktx" : 0,
    "difficulty" : 9.82679260,
    "errors" : "",
    "generate" : true,
    "genproclimit" : -1,
    "primespersec" : 3931,
    "pooledtx" : 0,
    "sieveextensions" : 6,
    "sievepercentage" : 10,
    "sievesize" : 1000000,
    "testnet" : false
}
in comparision here is hp10 on cent 6 , dual 2650s :
primecoind getmininginfo{
    "blocks" : 138482,
    "chainspermin" : 55,
    "chainsperday" : 6.34229883,
    "currentblocksize" : 1000,
    "currentblocktx" : 0,
    "difficulty" : 9.82675713,
    "errors" : "",
    "generate" : true,
    "genproclimit" : -1,
    "primespersec" : 6681,
    "pooledtx" : 1,
    "sieveextensions" : 6,
    "sievepercentage" : 10,
    "sievesize" : 1000000,
    "testnet" : false
}

you can only overclock it in single cpu configuration , not dual socket ! , what do you mean does it worth it , if it is 90$ a month , with current prices , that's unlikely to return the investment . if you are purchasing it , do you need it for any other reason ?