I'm looking for advice on how to get the most out of my servers, and am looking for information on the advantages/disadvantages of various strategies.

Right now, I have a production (ve) from Media Temple with 1GB and a development (ve) with 512MB. I'm running one installation of Magento, and get between 100-300 visitors per day. My traffic is directly proportional to the number of products in my catalog, so I know that as I add more products I will receive more traffic. Obviously, it's a humble little operation right now.

Last spring, I naively set up Apache with APC Cache and Varnish, not realizing that it wouldn't support SSL without further intervention. Since Nginx can support SSL with or without Varnish, and since it has such a great reputation for performance, I made the switch.

On the production server, I just have Nginx running by itself right now while I work out a better system. I installed APC on the dev server this morning, which seems to be helping with PHP memory consumption. I intend to install Varnish as well, and should attempt to optimize MySQL, but thought I'd consult the community before proceeding since I'm not completely confident in the path I'm on.

I don't really know how to weigh the pros and cons of creating a more complicated system vs. paying for a more powerful server. Nor do I understand at what point I should start considering memcached, load balancing, etc. There are likely more appropriate steps between where I'm at now and those solutions, but I'd love to have a plan of action established for the future.

Any thoughts? Any resources where I can further educate myself? Thanks!