Ogre with Yake or GOOF
Good Community Support, good community tools, but may not have the legs for a full fledged game or console port.
Nebula Device 2
Very High Learning Curve, fantastic engine, very powerful, loads of shipped titles. Buy the Maya Toolkit and you’re laughing.
Unigine
Pretty engine, runs badly on slower machines but has a nice feature list. It’s also a tad pricy
Beyond Virtual
Easy to use, fast to develop with, limited but growing feature list
C4
Another Growing engine
Irrilict and Crystal Space I have looked at but have no true experience to comment, feedback on both have been good.
With regards to your Network client, I’ll post more later, but I have some nice MMO clients and other Network tools
Look into the engines above and see what you think.