Netflix only requires 1mbps for 720 content, 2mbps - 3mbps spikes on 1080p content.
Although I have 1000' of Cat 6 strung through our home, we currently have only a 100mbps switch driving our wired network; With two Netflix streams running and a Vudu 1080p stream running the other day, streaming high def music (flac) in another room, we still had ample bandwidth to spare on the wired network and the wireless network was almost unused. Upgrading our switch would be the very last thing on my mind if it were on my mind at all.
We can also run any of the Netflix consuming devices on wireless - the result is indistinguishable from running on cable and utilizes the same bandwidth from the source(s).
Irrigation systems and WiFi thermostats are going to use next to zero bandwidth.
You might want to consider upgrading in steps, and tackling known problems.
For example - your problematic wired connection to the Samsung BD player - get that rectified! Your old 4 port hub - try disconnecting that from your network to see if there is a positive impact to other devices. Don't laugh, I've seen more than one of these old cheap dumb hubs fail and bring down network throughput.
As a first upgrade step, particularly since you've already mentioned wireless coverage is sub-par, consider replacing your wireless router. I have an Asus that I'd buy again in a heartbeat. A better router, with native or third-party software, may well give you tools to help you assess your wired and wireless networks. For example the graph above came from my router; I can look at the 2.4 and 5GHz wireless independently, the wired WAN and wired LAN ports as well. Even though we have the router sub-optimally located for whole house coverage (in the farthest recessed corner of our basement, mounted on our telecom wall panel), we get great coverage two stories up and all around the yard and garage.