I am ready to upgrade to a new tivo. I want as big a harddrive as
possible. I have two satellites- dish tv and direct tv. is tivo itself
the best place to buy? or are there other reputable wholesalers out
there?

If you want as big a harddrive as possible, have you consider
"hacking" your old TIVO?  This process voids the warranty, but if you
have technical knowledge, you can increase the harddrive size hugely
(upwards of 120 hours of storage). Check out sites like
http://www.tivofaq.com/hack/ and 
http://www.keegan.org/jeff/tivo/hackingtivo.html for some background
info to see if you could hack the sucka.  (FYI - TIVO uses linux, so
if you know linux, thats a big plus).  As far as buying a new one, I'm
pretty sure that 30 hours is the biggest you can get.  Places like
http://www.televisiondepot.com/tivo.html sell them, and here
http://www.usbyte.com/common/tivo.htm is a neat little article on how
the TIVO works.   -- Not really trying to answer your question, just
making sure you knew about the shadier side of TIVO, and the "hacking"
option.