[Hikarin]

Originally Posted by Lynne

You would need to center the whole userinfo area:

#sidebar_container.member_summary .blocksubhead {
    text-align: center;
}
#sidebar_container.member_summary .blocksubhead #userinfo {
    width: 100%;
}

And then if you don't want some centered, such as the name, then go:

#sidebar_container.member_summary .blocksubhead .member_username {
    float: left;
}

Thank you so much, it worked a charm! =D
The only thing I couldn't find though was how to fix the online status indicator here. It looks a little off in the middle, but if I try and move it left, it goes too far left where it is too close to the username. It's not like it's overlapping the name or anything, but there isn't that tidy space that it would normally have. Is there any way to fix that or do I just have to deal with it?

All other issues are resolved and this thread can be declared closed if no one has an answer to my final question.
Thank you so much everyone for your help! ^_^