Background:
I have a TViX box which allows me to play ISO files of DVD's on my TV. This device has a 1tb drive in and quickly became full so I built myself a NAS. The TViX has 10/100 ethernet. The TViX also allows me to define network drives which can be used to stream ISOs to the TV via the TViX.

My NAS has 4 internal 1TB Drives as well as a seperate boot drive. The NAS acts as a stoarage device for ISOs to play through my TViX and also as a general fileserver and an 'always on' downloader. It is running XP pro SP3 and I use RDC to administer it.
The NAS is built on ITX tech with a VIA EPIA SN1800 motherboard and features 2 onboard NICs. NIC A is gigabit and NIC B is 10/100.

The problem:
I have currently only used the gigabit NIC on the NAS to stream movies and do all my downloading with. But I find my download speeds are pretty crappy averaging around 5k/sec to 30k/sec when downloading while I'm watching movies.

I had therefore thought of incorporating the NAS's second NIC as a dedicated web connection. So the gigabit is totally freed up for streaming and file transfers etc.

This is a diagram of my current set up (with the dashed line between NAS and Router as the intended set up).

I am quite a noob with networking so I'm having problems getting my head around all this;
Would my proposed set up actually work?
Would it aliviate stress on the gigabit NIC for movie streaming?
Is it even possible to tell a program to only use NIC B to download with and how would I do that?

Any help info or advice would be appriciated  

What about connecting the TViX box directly to the NAS box on the gigabit nic and connect the 10/100 to the switch.  Hard set the ips for the TVIx connections to something outside your normal network numbers, say 192.168.0.x range.
This would force all internet activity through the 10/100 and only streaming to the TViX box on the gigabit connection.

 
Hi there
thanks for the reply.  
Its a nice idea but unfortunately has one problem - I would lose my gigabit transfer speeds to/from the nas/fileserver to my main computer.