You can compare the various TV boxes here and yes, Amazon Prime app is only available on the V6.
Assuming you have VM broadband (which is a requirement), your best bet will be to include the request for a box-swap as part of a contract renegotiation when the time comes.
I should imagine that TiVo > V6 swaps will still be offered then, but as time goes on - VM may start to encourage more customers onto the new V360 platform which runs on the new Horizon software rather than TiVo.
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