Hardware optimization using VMWare virtualization

Hello All:
I am a general windows user, not a person with expertise in either PC hardware or software.
I want to migrate to a new home PC preferably a DELL XPS system, with Vista Home Premium (64 bit), Quad Core processor, and probably some 8GB RAM. The purpose is to use this PC for all of my family,
- two boys (15yr, and 12 yr) who want do home work, web surfing in the name of doing the home work (l.o.l), and some times play some web based video games , and
- my wife who regularly do web surfing and watching some movies on-line.

I don't want to build a custom PC system from scratch, instead just buy a suitable system from DELL or some reputed company.

Now I want to use VMWare to do hardware optimization using this same PC, and multiple monitors, keyboards and mices, so that every one can use the same PC using different Virtual Machines on Vista Home Premium 64 Bit. To this end, I found a wonderful tutorial on this site.

[url=http://www.tomshardware.com/forum/237498-44-users-computer-tutorial][/url]

I need your help here in deciding....

(a) What kind of Video card I need to choose - integrated video card or a separate video card, video card memory size
(b) I hope I don't need multiple video cards, am I right ?
(c) Since I need multiple audio cards to support multiple users on multiple VMs, what kind of XPS system should I choose ? How do you know, whether a system accommodates multiple audio cards ?
(d) Any other issues I don't know

My Sincere Appreciation for your kind help,

Prasad Nutalapati