You said you had an xsi so I'm assuming you're taking that next step in gear. A D7000 + the 50/1.8G would be a great starter set assuming you will invest in a wide angle and telephoto down the road. Until then zoom with your feet!
I would personally go D7000 with a 35/1.8G. I find my 50/1.8G to long on most occasions on my D90. The 35mm however stayed on my D40 the entire time I had it. I loved that lens so much that I am planning on selling my Tamron 17-50 and my 50/1.8G and using just a 35/1.8G.