i've not been all that happy with hdtracks.
several months ago i purchased the 96/24 version of bill evans' waltz for debby, at that point the highest resolution version of that album hdtracks had for sale. then a few weeks ago i noticed that they'd released a 192/24 version, and i wrote to inquire whether hdtracks had an "upgrade" program which would allow me to buy the higher res version for the difference in price. the response from customer service was "no, because they're separate products."
ok, i understand that hdtracks is in the distribution business, and if that's their business model, fine. but knowing this, i will certainly hesitate to purchase anything from them which isn't 192/24.
my experience with eclassical.com has been much more pleasant. eclassical offers a full no-questions-asked money-back guarantee on everything you purchase from them, and -- although this shouldn't count for much, but in my case does -- the folks at eclassical are friendly, helpful, and quite obviously committed to their customers in a way hdtracks doesn't appear to be.