A dedicated server helps, although you should be able to run the script on any shared package without too many problems. I was asked to move from a shared/reseller account once because I was running many sites using mrrats script, but just one or two sites should be fine. My script also has a couple of 'fixes' in place on top of the ASM2 script.
As pilky points out be careful when using shared hosting for more than one large Amazon affiliate store! Though a number of smaller sites with a few ECS pages should be ok. I had the same problem with my account being closed for using too many "resources"! This was with a popular webhost that offers unlimited domains. Lost all my work on the websites I had hosted with them. As they would not allow me to access my account.
OK guys, I have put the script out. The download URL etc is in this thread: http://forums.digitalpoint.com/showthread.php?t=89940