Personally I really liked Sadler's QGD book, but I don't think I'm a very strong player and so that may be the reason it read well for me. I have played for about 10 years also, mostly online and against an old Novag tabletop computer(!); online I play mostly blitz (I know, bad for your game

) I'm afraid and veer wildly from 1700 to at best 1950 most of the time. Still, I've read quite a few books and I like all three of Sadler's that Andrew mentions, preferring the QGD over the Slav over the Semi Slav (in terms of the books, not the openings). I also have Chris Ward's White repertoire book on the Queens Gambit that you mention (and his QGA book) and although I don't like his writing style very much I think it's a useful book that you probably ought to buy if you intend to open this way. I didn't know it had received any derision here, but I bought it primarily for the extensive QGA coverage, as I play the QGA a little as Black, but it looks like it would be beneficial to White 1d4 players with the occasional caveat (Slav is not handled with mainlines etc, weighting of material e.g lots of QGA may be questionable to some).
It's easy to second Andrew's recommendation of Rizzitano for QGA coverage, and I also liked Bogdan Lalic's slightly older book on the Bg5 systems of the QGD, if you can still find it. That one had plenty of coverage of systems such as the Ragozin, Cambridge Springs, Vienna, that Sadler barely mentioned in his own QGD book, as well as covering Tartakower and Exchange lines (and Alatortsev). Also possibly of interest if you want a big lump of theory is Lasha Janjgava's Queens Gambit & Catalan for Black, although I personally found this strictly a reference work, there's hardly any explanatory text in it. Still, it covers the Catalan quite well.
John Cox's 1.d4 book is also in my library, by the way, and I would say this is a must for anyone who plays 1d4 (I don't) or anyone who struggles against it (I most certainly do).
Hope some of this may help.