Moved from old product to Extra - now getting much slower sync

[#1]

Hello,
I recieved an e-mail yesterday confirming the move from one of the old Plusnet products (Broadband Your Way - up to 8mb, I think it was. It used to sync at about 6500Kbps), to Extra - up to 20mb. The estimated speed was 13mb.
However, since this morning my router is syncing at about 3550Kbps and the IP profile according to the BT Speedtester is set at 3000Kbps. The actual download speed is a little below this. The downstream margin seems to be around 12-15 db, according to my router. This is with the router attatched to the master socket and with no extensions connected, although I haven't yet tried opening up the master socket and plugging directly into the test socket. Here are the figures from the router:
DSL Status: UP  
  DSL Modulation Mode: NOT TRAINED  
  DSL Path Mode: INTERLEAVED  
  Downstream Rate: 3552 Kbps  
  Upstream Rate: 444 Kbps  
  Downstream Margin: 13 db  
  Upstream Margin: 27 db  
  Downstream Line Attenuation: 25  
  Upstream Line Attenuation: 16  
  Downstream Transmit Power: 0  
  Upstream Transmit Power: 0
Is this slow sync speed something to do with the change to Extra and likely to improve, or is it indicative of a fault which just happens to have occured at the same time?
Andy.

[#2]

HI Andy,
Is your router compatible with ADSL2+? This will play a major part.
Jojo

[#3]

Hi Jojo,
It's a Linksys WAG54G v2. According to the data sheet on the Linksys web site it should support ADSL2 and 2+, although it is getting a bit old now.
I've been thinking about getting a new router with gigabit ethernet, so maybe now is a good time.
Andy