PS3MS works quite well but it would appear from your diagram that the route between the PS3 and the server is via two wireless links and this is probably the biggest part of your problem in terms of the amount of latency and overhead these links are adding to your media streams. Using only the kit in the diagram, your best option would be to get the server onto the same AP as the PS3 using one of its 4 switch ports.
If all the kit needs to be spread out as much as the wireless links imply and direct cabling is not possible, I'd replace the outlying APs with 200Mbit or 1Gbit homeplugs - you'll need 3 in total.
Edit: You could also use just two homeplugs - one to replace the AP on the PS3 and the other connected to the same AP as the servers.
I presume getting the PS3 on the RT-N16 via Ethernet is not an option? Because that would solve all your problems ;) – Tobias Plutat – 2011-01-23T22:10:17.927
Doh, yeah I can't do that. :( – Biff MaGriff – 2011-01-23T22:16:55.580