Well, the mobile tire repair guy just finished up. After speaking with him about the situation, I ended up keeping the HSR tires on the rear and will be returning the HDR's I just purchased to the shop. He basically said that the only difference between the HSR and HDR tires are the tread depth. Their construction is identical. He suggested that since there was such little wear on them, I should just buy a new HSR tire to replace the one that was losing air (which he found a screw lodged in). Otherwise, I would be spending a lot of money on new tires I really don't need.
Since he was out here, I had him check all of the valve stem cores on all the rims, because I've always had problems keeping consistent pressure in the tires for more than a few weeks at a time before needing to add air. He pulled the rear driver side wheels off and both of the inner valve stem cores were leaking, even after tightening them with the core tool. So I just had him replace them all around.
