I "upgraded" from the £17.99 Anytime package, with the speed touch modem, to the live box 2Gig package at no extra cost and get the free evening and weekend calls on the livebox.
Only did it so I could connect my laptop wirelessly from the garden last summer (Ha Ha).
If you have a BT line then you now get the free evening and weekend calls anyway from BT.
Your belkin router is probably better than the Live box.
The only advantage the livebox would give you is another telephone line (via the BB part of your normal line.