Answer to THE KING: I was on vacation, sorry for the delay.
The situation at top level is absolutely irrelevant to our choice of opening. It seems they all think that 1...e5 is the only correct answer to 1.e4 and they may be right. Even Delchev now is trying hard to master the Spanish. 
Now about the Kan - I have never played that nor have we discussed it with Delchev. There were several Bulgarian GMs playing it regularly and since my youth I remember that everybody considered Bd3, 0-0, c4 as awkward for Black. My personal opinion is that a normal Maroczy Bind - without exchanged pieces or lost tempi like Nd4-b5-a3 - gives White a lasting edge. In fact any spatial advantage which cannot be compensated with concrete play is an edge in itself. The stronger the opponent - the more oppressing is to defend such positions in a tournament. No wonder nowadays Black prefers in the Sicilian variations with ...e5. I'm unable to provide concrete variations though.   

What puts me off the Kan is 5.Bd3. If you prefer trench warfare to direct piece play, than the Kan should be your chioce over the Taimanov. A matter of taste.

I would like to ask Semkov if he thinks the Taimanov variation in his book is a better choice than the Kan (1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 a6) and why?

Which is the more trusted weapon at the top level?

Thanks

Today I saw the discussion about 13.c4. After only a brief look at the position, I must say that it seems very attractive for Black. The key point is that Black is very active! White saved us from the only problem  piece - the c8-bishop, and gave us a fantastic outpost on d5. As usual in this line, our primary concern should be how to activate the rook from b8. 15...0-0? may be good, but it contradicts this principle because after 16.Bf4 the rook should retreat to a8. What a shame! So the first move, which strikes, me is 15...a5. Perhaps it is best. Let ponder however over 15...Nd5!? In my opinion Black has an obvious initiative there. He should aim at doubling the rooks on the g-file or including the queen into play. The a6-pawn should be beyond our attention. Here are some variations: 
1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 Nc6 5.Nc3 Qc7 6.Be3 a6 7.Be2 Nf6 8.0-0 Bb4 9.Na4 Be7 10.Nxc6 [10.Nb6 Rb8 11.Nxc6 bxc6 12.Nxc8 Qxc8 13.c4 Nxe4 14.Qd4 Nf6 15.c5  Nd5 (15...a5!? 16.a3 Nd5!) 16.Qxg7 Bf6 17.Qg3 (17.Qh6 Ke7 18.Rab1 Rb4 19.g3 Qg8 with initiative) 17...h5 18.Rad1 (18.Bxa6 h4)  18...h4!? (18...Rxb2 19.Rb1 h4 20.Qd6 (20.Qf3 Qb8) 20...Be7 21.Qe5 Bf6=) 19.Qf3 Ke7 20.b3 Qc7 21.Bc4 Be5 22.h3 Rbg8 23.Rfe1 Rg7with initiative. 

Hello,

     Have looked again at 14 ...d5, and the line you gave, seems like you are right that white can cause problems there.
         What I did notice, when looking through Semko/Delchev book is that the 10c4 line can transpose to your game. In other  words after, 

1.e4 c5 2.Nf3 e6 3.d4 cd 4.Nxd4 Nc6 5.Nc3 Qc7 6.Be2 a6 7.0-0 Nf6 8.Be3 Bb4 9.Na4 Be7 10.c4, after 10Nb6 Rb8 is recommended by Delchev, 
10 ... Nxe4 11 Nxc6, the other approach were could give the story of keeping more "bits on" with 11c5 is more common in high level games, 
11 ... bxc6 12 Qd4 Nf6 13 Nb6 Rb8  when 14NxB QxB 15 c5 transposes to your game, whilst after 14 c5 d6 immediately is recommended. You could say that 14NxB is a typical lower rated novelty. Going to that effort to remove black's bad bishop does not look like an improvement. Anyway, it gives a clue that your play was fine up to move 15. Fritz suggests here 15... Qb7, so that if 16Bf4 Qb4. Then, one line is 16 Bd3 0.0 17 Qh4 Qxb2 18 Bxh7+ Nxh7 19 Qxe7 Nf6. The story now is white is not getting a bind, and struggling to find compensation for the pawn. It is amusing to look at the stories I put to bad moves earlier in the thread, suppose that's what weakies like me do. If the above, is at all close to the truth, then the conclusion is, your game continuation is an inferior version of the 10c4 pawn sac line. 
    It is interesting to speculate if your opponent was deliberately tricky, with moves like 10Nb6, or got lucky with a shakey memory of the 10c4 line  .
        At the same time at looking at this, had a quick look at 1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 Nc6 5.Nc3 Qc7 6.Be3 a6 7.Be2 Nf6 8.0-0 Bb4 
9.Na4 Be7 10.Nxc6 bxc6 11.Nb6 Rb8 12.Nxc8 Qxc8 13.Bd4 0-0 from Anand v Polgar. Later in the game saw the eye catching advice of, keeping the queens on, and staying completely passive. How often do you see advice like that  . Not suprisingly the main recommendation is the more active 13 ...c5.

Bye John S

Umm, thought I was showing some interest, and had made similar comments about  15... Nd5, and 10Nb6 before you. 
                  I could have put more analysis with 14... d5, but was making a judgement, that black was keeping the white square bishop under control, so looks the way for black to go.
                 Hard to believe that 13 ... Nxe4 isn't the right move. In the similar, 10 c4 line, in the first high level game Larsen v Karpov, Karpov avoided 10... Nxe4, but that looked like a typical safety-first reaction from him on seeing a novelty.(The Delchev book covers 10... Nxe4).

Hello guys; it kind of seems like I'm the only one interested in this line, but I'll share what I've looked at so far...

I no longer think 15...Nd5 is an improvement for Black, due to 1.e4 c5 2.Nf3 e6 3.d4 cd 4.Nxd4 Nc6 5.Nc3 Qc7 6.Be2 a6 7.0-0 Nf6 8.Be3 Bb4 9.Na4 Be7 10.Nb6 Rb8 11.Nxc6 bc 12.Nxc8 Qxc8 13.c4!? Nxe4 14.Qd4 Nf6 15.c5 Nd5 16.Qxg7 Bf6 17.Qh6 Rxb2 18.Bc4 Qd8 19.Rab1! White looks better.

I'm now starting to question taking the pawn right away, and think maybe something simple like 13...d6 (still threatening both the e4 and b2 pawns) is the right move.  Still, doesn't White look better with those nice Bishops and no weaknesses after something like 14.Qc2?

I must admit that I thought more people would be interested in this line, given the popularity of the Delchev/Semkov book.  This novelty (13.c4!?) strikes right at the heart of the repertoire!  Even if it isn't anything to worry about theoretically, I thought there would be more players who want to know the best lines for Black!?