Personally I think the single best investment you can make for opening theory is a subscription to www.chesspublishing.com. That goes for the Semi-Slav and any other opening, because the PDF ebooks are comprehensive and are updated every few weeks based on new games. It's also cheaper than most books.
Also be sure to explore the free Shredder Opening Database (http://www.shredderchess.com/online-chess/online-databases/opening-database.html).
A very new book is "Chess Developments: Semi-Slav 5 Bg5" by Bryan Paulsen. It makes me feel confident in the Cambridge Springs for the first time, and it covers some important new theory on the Anti-Moscow Gambit (my personal specialty).
That leaves the Meran System and sidelines. Dreev's "Meran and Anti-Meran Variations" is pretty disorganized but the material is good.
For you, based on your rating and that you're also interested in the Slav proper, I'd recommend "Starting Out: Slav and Semi-Slav" by Flear.
Appreciate the resources Reed. Was surprisingly unfamiliar with ChessPublishing.com As for needing opening databases I have membership at 365chess in addition to having MegaDatabase 2013 for CB so not quite necessary, but appreciated.
I'll definitely need to check out your recommended text by Fleer, and then see how much deeper I need to go. It's something i've tended not to need to focus on until lately, but i've reached the point where i'm unable to play in any but the open sections, and hence there will be greater and greater chances opponents decline to enter a Caro-Kann after d4, but rather a transposition to the Slav instead due to my stubborness about entering Caro-Kann (1. d4 c6, yes I actually play this for Black) and its structures, and it helps with supplementing theory for English play as White.
Granted mostly familiarity and plan comprehension are what I seek as then it's easier to home in on the anti, but forcing moves for such positions opponents tend to overlook the possibility of and which are hopefully the killers.
While i'm aware this isn't precisely the Books and Equipment section i'm hoping this isn't too far out there, and the equipment section usually remains pretty quiet as far as notoriety goes.
I need some quality material on the Slav and Semi-Slav. While I possess a few texts which refer to the Slav I only possess one which is dedicated to it, and my other two texts are dated or game examples.
Presently being
The Slav: Move By Move by Cyrus Lakadawala
and for the two texts which refer to it in passing a game book on Kramnik
Kramink: Move By Move by Lakdawala
Unfortunately these two aren't enough material on either, and especially the semi-slav.
The only other book I have on the subject which looks at the semi-slav in some detail is a rather high level opening repertoire book I picked up for cheap but it's from 2004 called
The Chess Advantages in Black and White by Larry Kaufman
Unfortunately these need to be reasonable dated books a year or two and older as the nearest store won't be getting the shipment of Avrukh's new book Grandmaster Repertoire 17: The Classical Slav until after i've already taken off for a very large tournament.