Looking for a decent gaming system

I've been looking for a decent gaming system within $800 and I've come across this custom HP Pavilion Elite e9200z PC system. I'm going to be playing World of Warcraft and I don't really plan to go much further than that(besides maybe their expansions). Do you guys think that this machine would be able to run it at medium to high settings with a good FPS?

Alas, here are the specs:

- Genuine Windows 7 Home Premium 64-bit
- AMD Phenom(TM) II X4 920 quad-core processor [2.8GHz, 2MB L2 + 6MB L3 shared, up to 4000MT/s]
- FREE UPGRADE! 6GB DDR3-1066MHz SDRAM [3 DIMMs] from 4GB
- FREE UPGRADE! 640GB 7200 rpm SATA 3Gb/s hard drive from 500GB
- 1GB ATI Radeon HD 4650 [DVI, HDMI, VGA]

Also I will be playing at 1920x1080 on a 24" monitor if it makes a difference but I can also downgrade to a smaller monitor if needed(But I'd prefer not to   ).

Thanks