Sounds like a reasonable price, don't pay more.
The DX11 is like many synths made then a 4 operator FM synth. Mostly sounds crapy but good for E-pianos and bright FM strings.
This model also has multitimbrality which should make it sound even better when you can mix different sounds.
You will probably search for third party sounds on the net because most presets from yamaha sucks.
Check this site out: http://www.sonicstate.com/synth/Yamaha_DX11.cfm