RunningMan: As fas as VDSL goes, mjb's correct - generally speaking 16dB isn't going to cut it for VDSL, but if you do flag up as being inside a VDSL area, it may pay to contact an ISP for a qualifying check just to see.
+1. Get a pre-qual done to check; from personal experience I'd recommend snap, though I believe unleash are also very good (business provider but they will sign up residential in some cases I understand)
EDIT: BTW, half bridging is a good option IMO. I previously had good success running an RTA1320 half bridging to router - they can be had on trademe for ~$5, fairly easy to setup and you obviously already have a router, so it'd be a cheap option to play with if you're having issues with the AM300 or just wanted to have a play (though I believe the AM300 works well for half bridging too) Hmm. though I don't see any on trademe now... maybe the old supplies have dried up.