If you confirm that the client page is slow at elaborating the huge amount of data, then that is the main problem.
The bottleneck may not involve Lightstreamer library at all, depending on which kind of elaboration the page performs.

Does your page only display pushed data on the screen through one of the provided Visual Tables?
Is the big flow of pushed data limited to the snapshots or is it continuous?

As a first attempt, you may force POLLING mode from your client. In polling, the client asks the Server for new updates only after it has finished elaborating the updates already received, thus forcing more filtering on the server side.
However, this is only beneficial if filtering is allowed by your subscriptions (i.e. RAW mode or the "unfiltered" flag are not used by the client).