Too many markers: how to make them server-side as a tile layer?

I am developing a web application for public transportation information using the Google Maps JavaScript API V.3 as front-end. But due to the large number of markers (transit stations) displayed on maps, client-side performance is pretty poor , especially panning the map (even though markers are dynamically loaded based on the map border).

For usability design, clustering markers are not an option. So I'm considering rendering these markers as a separate server side tile layer . Then maybe using google maps event onclick and onmousemove on the map object to simulate marker interaction.

The question is: what is a good approach to this? What service / API / software / server should I learn that can accomplish this with minimal overhead and learning curve? Could you point me to a starting point?

I checked the Google Fusion Table, but it does not allow customization of the marker image, so it is not an acceptable alternative.

My project environment: PHP CodeIgniter on Apache server as backend, PostgreSQL 9.2 + PostGis 2.0 as database system, all hosted on a small server with Amazon EC2 instances.

PS. My site is at www.bussup.com if you are interested (it is not international yet, so sorry for the lack of English support)