We are planning to release TwonkyManager on Mac next year.
When you say you want to add support for the Philips HTS9540. What do you mean? If it's a UPnP or DLNA-certified device you should be able to pull music from TwonkyManager/Server today. It won't appear in the Play Here section, because it's not a renderer. Not sure if Philips plans to add support for that later.