As far as I know from what I've read, you need a NTSC-U copy of QIIIA to play online, PAL and NTSC-J versions don't work (right?).
As you've been already replied to in the other topic, the only way to play non-JAP games on your NTSC-J Dreamcast is to region-free mod it or to use a boot disc.
DC-X is best for playing non-native/imported games, while Utopia v1.2 which is the latest version (there are v1.3, v1.4 and even v1.5 floating around but those are fakes, as in, they are v1.2), is best for playing burned games, while it can boot a good amount of imported games too.