if you need 656667.67 for masternode, you will have only maximum 38 masternodes
for better security and right now affordable for anyone - you should have more masternodes!
DRK is 1000 coins for master node and ~5 million coins exist - possible 5000 masternodes..
with that calculation - you need to enable masternode from minimum 5000 coins.

{
"version" : "v2.2.2.0 - Thymine",
"protocolversion" : 1001000,
"walletversion" : 60000,
"balance" : 302501.26200000,
"newmint" : 0.00000000,
"stake" : 17500.11500000,
"blocks" : 8407,
"moneysupply" : 24993010.83200000,
"connections" : 5,
"proxy" : "",
"ip" : "208.90.164.68",
"PoS difficulty" : 0.16326363,
"split threshold" : 1000.00000000,
"testnet" : false,
"keypoololdest" : 1431028800,
"keypoolsize" : 103,
"paytxfee" : 0.00000000,
"errors" : ""
}