I prefer a softer species for the benchtop - its easier to work, easier to maintain & less likely to damage projects you place on it. And likely cheaper than hardwoods.
Douglass Fir is excellent -if you can find old growth with tight grain that would be ideal.
For a spilt top, see if you can find some 12" x 4" - maybe from a demolition center/timber recycling supplier.
While not quite a traditional design, see my bench renovation project pictures here - I have a 12x3 as the main bench surface.
http://www.woodworkforums.com/f213/b...ovation-205992