$5000 is too much to spend reasonably today.
Budget $1000 or so for a 30" monitor; it will last you for a long time.
Next take $2000 and invest it for a couple of years. Plan on using it to replace or upgrade your build.
The remaining $2000 can build you a top of the line gaming machine for today.
Base it on a 2600K, sli GTX570 or GTX580, 8gb of ram, a SSD for the OS and apps , a Quality 900w psu,
Buy a glorious looking case, it will last you for several builds. Check out the lian li cases.