When mine switched over from nildram to sky today, my old DG834G could only manage 10Mbps with 6dB noise margin, whereas the DG834GT manages 15Mbps with 14-17 dB margin, so there can be a huge difference in changing router
If yours isn't great, perhaps take advantage of a shops money back guarantee, eg Argos?
Kris
Sky Broadband
Ashington (Northumberland) Exchange
Netgear DG834GT