Hello,
Here is the link to something called DSP calculator:
http://www.cisco.com/cgi-bin/Support/DSP/dsp-calc.pl
This calculator will help you to determaine the exact number of DSP's required for your setup.
As for the dial-peers , the dial-peers are limited with the RAM on the router , you have to check how much exactly the IOS takes from the RAM (Check the release notes of the image) and add at least 128 - 256 for CME , dial-peers , etc.... i am not really sure if there is a calculator for this but this usually what i do.
Amer