The long and the short of it is… you should really find a company that you trust. Or, spend the time getting the information that satisfies you so you can decide on your own. Any advice you get on-line should be weighed right along with the advice you’ve already received. Your question about component vs HDMI likewise can be viewed multiple ways.
It is possible that the company you got a quote from has included all the parts needed to make a stable, long lasting system. One they are willing to standby and support for the long haul. Should they be viewed as any less competant than a company who comes in next and says it is a waste?
HDMI is the direction things are going for sure. But most importantly - find a company you trust and then, trust them. Otherwise you’ll drive yourself nuts second guessing each decision. It sounds like your technically inclined, so that might be tough. Use that interest and knowledge to identify someone who does things the way you’d like. Continue to understand what you’re getting, but don’t let it become the cog that keeps you from getting a house dialed in.