The Slav is a good choice, I´ve played it for several years as my main defence to 1d4.

Looking at your posts, pingudon, I think you should consider a few things before delving into it:

You cannot measure the theory volume of an opening. Especially not by counting ECO Codes!
The distribution of Eco Codes is based on grandmaster and master games ~1950-65, a lot has 
changed since then (the whole Sveshnikov in B33, Najdorf Be3 in B90, but D08-09 for Albin and 
D60-69 for old and today not much played QGD Capablanca!?)
 
And is the Slav really only D10-19 ?! - It´s really useful or even necessary to know something 
about the Semi-Slav (D43-49) or the Grünfeld Schlechter (D94). And 3.Nf3 Nf6 4.Qc2/b3 usually
transposes to QGA (D23). Or even to QGA mainlines (D26-29), look at Topalov-Kramnik game7.
And 3Nf3 Nf6 4Nc3 dxc4 5g3!? e6!= is a Catalan Gambit (E0?). And ...

To play the Exchange Variation for a win is a problem. A problem that can be solved, but of course it´s
a problem that requires experience and playing strengh.

The same about Queen´s Pawn Openings (Colle, Torre, London). After 1d4 d5 it takes a little bit longer
than after 1d4 Nf6/f5/... to create winning chances. Btw, D00-05 also belongs to a slav repertoire.

Nevertheless the slav would be a good choice. I would recommend Slav or Semi-Slav but not ...a6 !
That´s nothing to do with the soundness but in my opinion the a6 system looks easy to play but in fact
it is much more complicated and sophisticated than 4...dxc4 or 4...e6. Anybody should have much
experience in Semi-Slav and QGD systems before entering the world of ...a6 Slav.

tracke  

1) I have played both the slav and semi-slav as black. (Neither at the moment.) My preference goes to the semi-slav as I have difficulties getting excited by a bishop on f5 or g6 which doesn't do very much besides getting exchanged. A bishop on b7 at least have the possibility to do something.

2) It's not obvious how to get the semi-slav as 2...c6 allows the exchange variation, 2...e6 and 3...Nf6 allows regular QGD and 2...e6 and 3...c6 allows Marshall gambit.

3) The Nc3/e3 variation vs the slav can be met by 3...dxc4. There's no need to learn the Meran and anti-Meran for that move order.

The exchange variation is not a good reason to stop playing the Slav. But that depends on your need to win with both colours of course. Anyway 1. d4 d5 2. c4 e6 3. Nf3 c6 4. Qc2 is not much easier to win from the Black side than 1. d4 d5 2. c4 c6 3. cxd5. 

Regarding Slav v. Semi-slav, the crunch is in the critical variations. Compare Main Slav 4... dxc4 5. a4 Bf5 6. Ne5 and Botvinnik/Moscow Semi-Slav. I will consider Black side of 4...dxc4 5. a4 Bf5 6. Ne5 marginally easier to play for beginners than the Botvinnik/Moscow, but against stronger players (>2200), would say Botvinnik/Moscow is a better bet for club players since its easy to drift into passivity in Main Slav (how many people can play moves like Rg8 a la Kramnik?!), and the better lines for Black in the Main Slav (which you should play against stronger opposition) are slightly counter-intuitive...for example Morozevich's 11... g5 is surely more counter-intuitive than the Botvinnik Semi-Slav, which imho is a fairly predictable opening in comparison (!).

The Semi-Slav avoids the Exchange Variation, which can be annoying.  Other than that it's a matter of taste I suppose.  The Semi leads to greater complications and "unclear" positions more often.