i purchased my first slr about a month ago. i went to a place called adorama in the manhatten. i baught a canon eos 30d body and a canon 50mm f1.8. the lens is awsome but i needed something more universal. so i met up with someone from craigslist and baught a sigma 28-70 f2.8-4 for $100 (not a great price i know). should i just not use the sigma lens and try to shoot with my 50mm as much as possible? or only whip out the 50mm at night or when i want to do macro shots? i listed the thread as i need a lens because i want something good and ive been looking at the tamron 17-50mm f2.8 ($420) ..... and im open for sugestions for a awsome lens that isnt tooo expensive. ill eventually be shooting sports sometimes and just like taking random shots. and feedback is great. thanks!