I guess I am digging up an old thread but the OP was looking for the opinions of owners and players of Halo Basses, so hear I am.....better late than never I hope.
I happen to own a pair of Halo GVKs, A 5 string Bass and it's guitar bretheren. I have owned both since 2006, the GVK-5 happens to still be one of my main players. I have noticed that Halo doesn't get a lot of respect around here, however mine have been great.
XtheDeadPawn asked if they can hang with the big boys, I think so. I happen to own a couple of the basses you mentioned.....and the Halo has it's place among them.
I happen to love the tone of this bass, mine has dual MM style humbuckers and it's just massive. At first I expected to swap out the pickups for active units, however I was pleasently surprised to find that the tone and output of the stock 'HaloBuckers' were actually exactly what I was looking for!
If you still have any questions XtheDeadPawn feel free to ask.