If you're looking for a nice, sharp and affordable lense, i'd go with the 50mm 1.8 prime lense. Its crystal clear, and only about $70. If you want a little more durability, 2 more leaves in the shutter (for a total of 8, which will give a round halo for bokeh rather than a hexagonal one), and a little faster focusing, i'd go with the 50mm 1.4 (runs about $300). The 85mm is just as good, though its mostly an outdoor lense because its so far away.
I prefer prime lenses myself, because they are so so sharp for portraits.