You might want to check out the Jamis Coda. They are decently priced flat bar "go fast" bikes with a MSPR of $440. Many on this forum love them. I had one of the first models they ever made and loved it. A friend of mine still rides it to this day.

BTW, stay away from cheap suspension seatposts, they don't work well and break quickly. You might want to consider a seat with springs as an alternative.
http://www.jamisbikes.com/usa/bikes/06_coda.html