I built that DVR computer myself.
back 2 weeks ago, i was using a Pentium4 1.6GHz with 256mb ram for running 5 cameras live.
I wanted something more silent without fan, so i upgraded to that :http://www.newegg.com/Product/Product.aspx?Item=N82E16813121442
With only 2GB Ram and it's doing the job very well with Geovision Software
You can try using one of them Multiple Display Boxes, but they're not going to be that cheap I think.
Well i found some of them on ebay for less than $30, and newegg are selling one for $45
I just want to be sure there won't be signifiant quality loss like i had with a traditionnal "Y" vga splitter