TRUST ME you do NOT need to be handy at all to build your own computer. I have no experience with doing it and I built my current machine.
I bought all my stuff off newegg, including a 22 inch monitor for about $1500 after the rebates.
I have 4 gigs of ram. But watch out for windows 7. I loved the OS but when I tried to record I would get all these clicks and pops that would not go away. Went back to XP and all is candy.
What cost a big chunk of mine as well was a good graphics card. If you get a cheaper one you can significantly lower your cost.
Do you need monitors / speakers? If you're going to leave this computer in one place, get a bigger case so you get more air going through it as well as more room to move and put in different things if need be. (some smaller cases can't fit certain boards)
your questions, my answers:
4 gigs of ram
windows xp (it could have just been an error with my soundcard and the OS)
no. firewire ftw!
yes, around $1,000 give about $200 I'd say.
your final thoughts, my .. thoughts:
online company to what? build the computer?
will be VERY easy and MUCH cheaper to build it yourself.
all the cables and wires can only go into one place essentially, and there are plenty of guides online on how to do it. It's honestly "put this board in this slot, attach it to the power supply" and that's it.