If I might suggest "Easy Model" as a source for your 20MM armor. A tank ready to go out of the box at not quite the price of a Dragon die cast. I would also see if a google search would turn up "wargame tank kits" as a viable option. Some kits out there that are bare bones but you get two tanks per box and cheap too. Built for wargaming, you just add the details you want.
Automatically Appended Next Post: Since you are going 20MM I also have a suggestion for basing your infantry. Use a movement tray that has holes cut for individual figures. I think Litko has them as well as a few other manufactures. If you want some opinions from folks that have used them you can go to
http://theminiaturespage.com/ and ask there.
Basicly it will allow you to use your figures for
FOW and other systems out there where you use the individual figures to play.
I would post up links to companies for you but I am not 100% sure that it is acceptable practice here.