For capture and running of all the software, I'd suspect 4 GB would be fine. But, if possible, go more. This hobby is always changing with respect to software and what not. Nothing wrong with future-proofing yourself.
I'm running TheSky6, MaxIm DL, FocusMax, RoboFocus, Gemini ASCOM, CCD Commander, and TeamViewer on a ten year old Dell Inspiron 9200 that has just 2 GB of RAM and is constantly running at 90% CPU utilisation. It just gets by. Time to upgrade, too.
H