What sort of views should I be getting (Mars/Tasco) ?

Hi,

I haven't used my scope in quite some time but thought I would set it up
to take a look at Mars. Am not sure what I was expecting but it wasn't
as good as I thought it was. I started out with my 20mm eye piece and
found the moon then from their found mars, then I swapped to my 4mm
eyepiece and I didn't really see a lot. By using the focusing knob I can
get Mars to go from a ring with a black dot to a small dot back to a
ring with a black dot.

My scope is a Tasco 450x112mm Astronomical Reflector, is it just not
powerful enough to get decent views or am I doing something wrong ?

What do I need to get views like these -
http://www.geocities.com/andreatax/Mars_2003.htm ?

Dave