Computer out --> coax distribution system

Ok so im trying to set up a pretty complicated system to distrubute 2 channels across the coax in my home so those desktops will be viewable from any tv in the home by tuning to a certain channel. Lets start with what I have in set up alreay (lets just focus on 1 computer & 1 channel, if i get that working, i can replicate it on the 2nd)

Computer:
Ubuntu 8.1
2.4 ghz p4
4gb ddr ram
4.5 TB internal sata storage (all my movies & such that I want to be able to play and view on any tv in the house)
GE Force 5500 graphics card (vga, s-video & dvi outputs)


Currently, I have the dvi going to a local display and the svideo out going to a linear rf modulator before the coax spliiter that distributes coax to each room in my home. To test the system, I am using a crappy channel 3/4 modulator ($30 bucks at radio shack) and plan to implement a nicer rf modulator with a notch to clear out the channels I want to use...so my first (and probably easier question) is can someone recomend a decent rf modultor that will run a minimum of 3 channels with flexable selection of what channels it output to?

The biggest problem I have is the quality of image is really poor and since I want to use the computer as movie server, it needs to be a decent image (not necessarily "HD" but something at least equivalent to standard TV programing). My first thought was that the cheap rf modulator was causing this problem, so I hooked a tv straight to the s-video feed on my computer and it was no better, so the rf mod is not the problem (it might be once i get a better output going, but ill cross that bridge when I get to it)

I have spent days reading online just to get to this point and getting very frustrated with it all. The potential solutions I am considering & questions I have related to those options are as follows:

Potential solution #1:
use the vga output through some sort of conversion to the rf modulator

from what I have seen there are cables that go vga-->rca video and there are converter boxes that do the same and are a bit pricer, one would assume the boxes will output a higher quality picture with more flexible options, am I right? If so, would the simple cable conversion be sufficient? If not, could someone recommend a reasonably priced converter box?

Potential Solution #2

do the same type of thing as in the previous solution, but will the dvi output....my questions are the same but related to dvi conversion

Potential Solution #3

I am sure it is possible that I am overcomplicated this or going about it complete wrong, so my last solution would be to take any suggestions you all have to create this system. Again, that system needs create tv channels (preferable with choosable numbers) that are the desktop of my ubuntu 8.1 movie server and do so in a higher quality than my svideo output is currently providing

Any suggestions would be great, Im sick of reading through thread after thread trying to find solutions, so I thought I would give it up to the AV gods and see what ya'll can tell me, thanks for the help!

PS I have a somewhat limited budget, but am more conserned with the system working (ie ide rather spend $400 on a system that works than $200 on something that half works)

I am not totally set on using any of the equipment I have and open to buying new equipment if necessary. From your reply, it seems like there is no way to distribute a decent quality image to all the tv's in my house? Again, I dont need hi def, just something reasonable. Currently I cannot even read the text on the screen it is so bad, despite the fact that it is outputting at 1024x768 which looks fine when I connect a monitor via vga at the same resolution. I can completely remodel this system if necessary, any suggestions?

Thats all well and good, and I suspected that the modulator would have quality issues, so as I stated in my original post, I pulled that out and currently have my svideo out straight to my tv and the quality of image is exactly the same, so while im sure you are right about the modulator, its cant be causing the problem to the tv. And 480i would be fine, what I am seeing is just terrible, very low resolution, cant read icons on my desktop, ect.....

well somehow cutting the output resolution back to 720x480 worked, i suspect when the higher signal was introduced to the rf mod, it screwed things up. So my video now distributes throughout the house and white its not high def, its good enough for whats coming from my computer. I am still open to any ideas for distributing a high def signal to multiple tvs in my home as I have 8 tv's and dont want to pay for comcast hd boxes on all the tv's and would like to have 2 "community" boxes that the tv's can use. I realize only 1 box can be in use at a time, but most of the time I wont need it. I got the IR side of things figured out, just need the video distro system, any thoughts?