Great to see the Kalashnikov generating lots of concrete discussion - and good too to see it featuring in the update for the second month running.
I’d be really interested to know which 6 c4 line(s) people think might offer the severest challenge to Black. Black’s move order, of course, might be critical here. It seems for example that the 6 …Be6 7 N1c3 a6 8 Na3 Rc8!? order is really neither more nor less than a cunning transposition device, Black in effect saying to his opponent “I’m going to steer play into one of the well-known 6 c4 Be7 lines - just not, perhaps, one you were reckoning on or were prepared for!”. Thus:
I 9 Be2 Nd4 10 Be3 Nc2 11 Be2 Be7 12 0-0 Nf6 13 f3 0-0 transposes to 6 …Be7 / 9 Be2 Nd4 etc.
II 9 Be3 Nf6 10 Be2 Be7 transposes to 6 …Be7 7 Be2 Nf6 8 N1c3 a6 9 Na3 Be6 10 Be3 Rc8 (How frequent or esteemed a way this is of meeting 7 Be2 I have no idea, and would welcome advice!)
III 9 Nc2 and now:
(a) 9 …Nf6 (9 …Na5 10 b3! b5 11 Nc3 is better for White?) 10 Ne3 Be7 11 Bd3 0-0 12 0-0 Nd7 (12 …Nd4!? is also interesting and OK?) transposes to 6 …Be7 / 9 Nc2 Rc8 10 Ne3 Nf6 etc.
(b) 9 …Be7 (the simplest?) transposes to 6 …Be7 / 9 Nc2 Rc8
In each of these cases White has alternatives, but not it seems advantageous ones. I find (II) above particularly fascinating. Here after 10 0-0 0-0 Aagaard/Pinski recommend (a) 12 Rc1 h6 or 12 …Nd7, or (b) 12 Qd2 Ng4!? since 12 …h6 13 Bd3! (rather than 13 Rfd1 Ng4) might allow White an edge. Years ago I spent ages looking at a line Silman gave in his ancient (1991) book: 9 Be3 Be7!? 10 Qd2 h6 11 Rd1 Nf6 then …0-0, …Ne8, …Bg5. Nowadays, of course, as A/P tell us Black plays …Ng4 rather than …Ne8 in these positions, so perhaps Silman’s line can be rescued: 12 Be2 0-0 13 0-0 Ng4!? and we’ve reached (b) above with 12 …h6 13 Rfd1 Ng4, with the sole difference that it’s White’s QR not his KR that’s on d1. But Black could also feint at Silman’s line with [9 Be3] Be7 10 Qd2 Nf6!?, aiming at (b) above and bypassing (a). Again White has other options, but are they dangerous?
Yes, I'm enjoying the Kalashnikov!