It depends, first on how many other device you have on your home network and two, if you have routing layer 3 switch that can handle the routing between the VLANs. You are talking about separate IP VLANs? If so the biggest obstacle would be have a device that can handle the routing which home residential router typically do not have that kind of power or physical capacity to do such.
If I had the type of hardware I have at work, I would put each pair of tivos on their own tagged vlan and then route them into the normal network but with doing such requires enterprise hardware that I can't justify the expense.
With adding VLANs you will need of course a dhcp server that can handle multiple in subnets if you want to distribute it addresses by dhcp but in a small network you could always apply static addresses.
Considering the bandwidth needed, personally unless you have a very large home network, the cost versus benefit would be small but and doing such would seem more a bragging right thing rather than increase performance. I run a couple routed VLANs on my home network but it's more just a showoff thing and not out of need.
So sure if you have the $$'s for the hardware, the bigger bigger issue is that despite the idea of establishing VLANs, the bottleneck remains the Tivo. Only the latest Tivo models have decent though put to their network adapters, you will not see better transfer speeds with MRV content simply because the Tivo can not overwhelm the network interface, just because TiVo's have a 100mb, they do not have to means to utilize such.
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