Yes, provided you have a monitor allready...
A 'state of the art' gaming system requires:
AMD AthlonXP CPU (Model 3000). Buy the 'retail box' version that comes standard with AMD's pre-tested fan...
Motherboard with NO integrated components. Onboard video is a sure sign of a junk board...
NVidia graphics card, latest revision, 128 MB RAM. Avoid the 'MX' variants, and anything lower than GF4 is obselete...
512MB or more DDR400 Memory
For a monitor, use a CRT not a flat-panel. Cheaper, and you get a better picture when dealing with fast motion...
Also, avoid Windows XP. There's nothing in it that justifies the purchase, and it adds a whole bunch of problems...
As for cases, any old case will do, as long as it has a big enough (350-400W) power supply. $25-75 is a good price range, buy this locally (from a small storefront dealer. they have the best prices) to save on shipping... Make sure it's a 'Full ATX' (BIG) case (3-5 CD-size (5.25") bays), since small cases create problems with fitting drives in and motherboard installation (because the components don't clear the power supply), and can cause cooling issues...
To get the best price, use [url]www.pricewatch.com[/url], this will find the current 'low price' from a wide range of small shops that sell through the internet... Don't buy from a retail store, esp CompUSA, Fry's, etc...
I'll guess $1200-1300 with a good 17 or 19" CRT monitor...