lchiu7: But for some reason no matter what size grind I use or what beans, the coffee comes out with lots of crema - much more than I see from commercial machines.
This might be typical behaviour from inexpensive machines with dual-wall (aka "pressurised") portafilter baskets:
http://www.espressoschool.com.au/about/faq/28-basics/13-unpressurised