I'm surprised to learn the Premium Tributes are not string through while the Standard models are (you'd think it would be the other way around).
As far as I know, the current US made G&L models all have a string-thru bridge. I have an older G&L ASAT bass without the string-thru option. I have to tell you, my ASAT rocks! Sure, the string thru option would be nice but as far as I can tell, it doesn't make a damn bit of difference. And for what its worth, the current Music Man Stingrays doesnt have the string-thru option either.
Just this past weekend I tried out a few 5 and 4 string Tributes. They were all Premium models (I didn't think to even see if they were string-thru or not) and I have to tell you, they blew everything away even remotely in that price range. The necks may not have as a refined feel of the domestic model, but at half the price or even less, why quibble, right? And hell, you even get a pretty good gig bag to boot. Honestly, I'd been trying out various basses at shops all over central Massachusetts all day before I came across this one shop with the Tributes and I have to say, I was totally blown away by them. Yes, string-thru would be nice, but its hardly worth brushing them aside for not having that option. These basses are excellent buys and I'm certain that I will be buying one as a backup to my ASAT and if I finally take the plunge to a 5-string, you can bet it will be a Tribute. I even fell in love with a couple of their guitars too.
Good luck,
r