5
You might want to verify that your PHP isn't using zlib output_compression. () to find out. That can give the same trouble as gzip.
The accelerators speed up PHP by precompiling the code so it doesn't have to be done at each call. It doesn't compress the HTML stream.
Two freebie accelerators I use are
Zend's Optimizer and
MMCache.
And the one I use in production:
MMCache. The author has taken a job at Zend so they are still in transition. The original site with a working version is
Here. It is Smarty friendly and so far no trouble.
You need access to the server's PHP so if you're on a hosted server you might be out of luck with these. But mmcache gives me a noticable speed improvement.