If you are not seeing the performance improvements you desire with wp-super-cache, then the other caching plugins are not going to help. All of the caching plugins basically do the same thing, they create .html files bypassing the PHP parser.
To improve performance, I would go down the list of best practices found here http://developer.yahoo.com/performance/rules.html
The rules that I think are the most important are:
- Use CSS sprites, reducing the multiple http requests will helps
- User mod_expires and mod_deflate Apache modules, this is critical
- Place your script tags after your css link tags
- Use ySlow in Firebug for profiling
- Check your HTML code. If you have several nested tables, the browser has to render the deepest table first, and then build out.
- Minify your CSS and JS. Minify is a great library.
If you chose to not use a caching plugin, make sure you have a PHP opcode cache, like APC. This means that the PHP parse runs only once, and not every request. This can increase your PHP performance by 2X.