Ok now to answer your question.
1)Your Going for a Asus/Msi/Dell Build
(For The Asus)
These MIGHT not work if you live outside the US/Australia.
(Ships to UK/Europe)
(sometimes Ships to World-Wide)
(Sometimes ships to World-Wide)
Overclocking can be done on ALL of the Asus/Msi/Dell Desktops.
Moniters come with them
and they are mostly under $900.00 (Depends where you live again)
It all Dpends on where you Live.
Also MOST of them will have Good graphics cards and Good Moniters Sizes
ASUS (RECOMMENDED BY ME)
EDIT:i just sore your Comment ok your going to want to go with www.newegg.com
(That WILL save alot of money)