You'd be very fortunate to get $350 USD out of that system. I'd ask that and see what bites you get. Also, what kind of condition is everything in? Have you kept it dust/lint free and clean? How many estimated hours of usage? Was that CPU overclocked? Keep in mind that CPU architecture is nearly six years old now (hard to believe it's been that long).
This is one of those things where you have to find the right buyer (and who either can't or doesn't want to build his/her own inexpensive brand new quad core rig around AMD's chips for just another couple hundred). In any event, good luck! I decided to hold on to my four year old E8400 4.2GHz overclock build after finding out how little I'd realistically get for it...it was worth it to me to keep as a backup rig.