I see i know stuff about the Essence series and the X-Fi PCI series and the TitaniumHD, dont know much about the EVGA, Onkyo or the Auzentech..
Essence cards are the same, i mean the C-Media Oxygen HD chip does not support PCIex, so the STX was made with some PCI>PCIex bridge chip too, but they did fuck up something with the clock gen there or something, and they fixed it later with the STX II.. So is not only the EVGA with bridge chip, but people like the Essence series very much, unless they want to game or something more then just listen to music and movies (BTW the Dolby the Essence have is really good for movies, and the other effects), for me the Esscence series is very very good for HI-FI audio and home cinema with the effcets, but for games is ok, is far cry from the X-Fi`s abilities on supported games (not that this matters after windows XP anyway) . Is interesting to me, that u find the ZX (i look only the high end cards that would be ZXR for me) good sounding card as sure the components used on the high end ZXR are very good same quality as the Xonar Essence series, i was fan of the ZXR and wanted to find one for cheap, but then did talk with another retro collecto enhusiast, and he told me that the damn ZXR does not have audio processor such as the X-Fi, but rather process the audio via software, and that made me not to want to have anything with the Z series of Sound Blaster... Another guy that did have both X-Fi TitaniumHD and later he did buy Sound Blaster ZXR, he did put to sale the ZXR very fast, he said the ZXR sound way worse for HI-FI audio...
But everyone is different i guess.