[bitfolk] Specs & Performance Question

Hi there, I'm in the process of setting up a fairly basic Apache2/mod-ssl/mysql5/ Drupal ecommerce site, and am seeing fairly horrid RAM performance on my VPS. I am working on figuring out my Drupal/Apache configuration issues (of which there are several), but while I can probably get the memory usage to somewhat tolerable levels, I would be grateful to hear from people who have similar setups what sort of minimum memory specs you recommend for 5-10 Apache processes? I have no problem figuring out what 'd theoretically need, but it would be very cool if anyone could share their real-life experience on what they'd recommend to be safe. Thanks, -John