For a high budget build like this, AMD is not what you want. Unlike back when that system was built (late 2005, early 2006 I would guess), Intel are the current performance leaders, and for high-end systems, they are by far the best CPUs to use.
I would generally recommend a Core i5 750, a Gigabyte P55A-UD4 motherboard, 4GB (possibly 8 if you think you need it) of Corsair XMS3 RAM (1600mhz, CAS9). This is a good backbone for any high-end system.
750W is ample power for a high-end PC, your current system only uses around 190-210W at full load, and the new system will not change that unless you upgrade the graphics card. However, if the unit is a mediocre brand (unlikely for the price you say you paid [I'd be amazed if it really did cost that much] but still possible) then it should be replaced.
It's worth pointing out that although a new CPU/board/RAM will improve performance in general applications, you will see only a moderate increase in games performance until you upgrade the graphics card. There is no reason to spend anywhere near $1400 on the system without a graphics card.
Lastly, building a new system will require you to, at the least, reinstall windows. Typically I recommend people get new hard drives in these examples even when they already have them, as this means they have a drive to start fresh with, without having to figure out where to backup all their files to so they can wipe their old drive clean.