I believe you guys are making your estimates based on an old world record.
The 1857 difficulty corresponds to a 559 digits 6-tuplet found in 2009. The present record, according to Tony Forbes, is 593 digits or a difficulty of about 1970. The record 6-tuplet is

219946485329 * 1399# / 2 + d, d = −8, −4, −2, 2, 4, 8, found by Serge Batalov in December 2013.

Tony Forbes' k-tuplet page may be found here:

http://anthony.d.forbes.googlepages.com/ktuplets.htm

But as (1973/1441)^9 = 16.9 using gatra's estimates, we should be able to beat the record with an extra digit within an hour or so. The Primecoin lot have broken quite a few world records, it would be nice if we could get some too.