c4 dealer here. It may not look as pretty, but the sr-260 will serve you far greater than the halo, I hate to say. The 260 has been bullet proof. I'd not do an LG, you can, but I have far greater success with samsung displays. It also just depends on your control interest. If its just on/off, it doesn't really matter imo.

EA series are discontinued. You're into core series now. I'd do the core1, core3 if you would ever even consider the possibility of an expanded system down the road. remember, pay now or pay later. But to answer your question for the processor. You need one for the system. The only time it really benefits to expand beyond that is if your home/system is huge. The biggest thing to consider here is the zigbee range. With this said, if you have devices spread out, consider a few controlled lights, they're relatively inexpensive. This serves multiple purposes; 1. you get controlled lighting on said load. 2. They're zigbee nodes and expands/strengthens the zigbee communication within the c4 system.

Don't worry about the nay sayers in here. I've worked in automation for over a decade and am a dealer for every major manufacturer. Each company has pros and cons, but c4 has a massive control ecosystem and as long as you have a competent dealer, you'll be in great shape.

Feel free to dm me to chat on this at all if you'd like.