I agree. I have a bluray player, and Apple TV 2 and a Roku HD. The Apple TV and the Roku are fine for most uses. I watch a lot of TV on them and some movie rips and they look fine. But, then there's bluray....
Bluray delivers a bitrate that can exceed 50 mpbs of video and sound. It is an incomparable system to the Apple TV or the Roku. Their downloaded movies and tv shows max out well under 10 mbps, roughly 6-8 mbps on average, in my experience. Now, that's enough for a decent HD movie and a stripped down 5.1 sound experience. But, there is a tremendous amount of details lost in both the sound and the video to reach the instant playback target the streaming systems are optimized for.
I will say that I've got a better than average home theater system with a Nad t747 av receiver, Infinity Primus floor standing speakers and a 10" powered subwoofer. So, the increased quality in the sound going from 2.0 stereo to a DVD is apparent. Going from that to the lossless audio in the Bluray rips is a real treat and makes my system just come alive. The streaming players have decent sound but never enough to make me want to really crank it up like I do my blurays.
Now, like the post I quoted suggested, buy the blurays, rip them and store the uncompressed rips on a large storage array. Then you can downmix from the highest possible content you have access to on any marketplace. Oh, and lest I forget, there's an ample market for used bluray movies. You may find that your total cost is actually lower than buying them from iTunes once you've sold the movie on the used market.