CSS sprites and JS minification are good general techniques, but hacking them out of the default Magento installation makes them a less-than-stellar option. You're likely to get better performance for your effort by enabling expiration dates on your files (CSS/JS/images can be cached for a while, especially once you've finished development) and making sure that apache gzip's those files. This will reduce the size of your page loads on empty cache and reduce the number of HTTP requests on cached pages.
After that, (and also recommended on the other topic mentioned) I'd recommend looking at the use of a PHP bytecode cache such as xcache. Magento loads many PHP files on every request, so such a cache will lead to significant improvements in performance. Ask your shared host whether they offer any such cache.
Also, here's the Magento article on performance, which has some good suggestions:
http://www.magentocommerce.com/blog/comments/performance-is-key-notes-on-magentos-performance/
Edit: Forgot to mention, block caching can significantly reduce the amount of time that Magento churns on a page, speeding up your page loads. Google magento block caching for some good resources.