I have a few years old Samsung TV and it plays near anything over DLNA (stream over TCP/IP from your PC), though you have to do some searching to find the right DLNA server and setup. Serviio works best for me. Buffering at movie start may be one or two seconds but certainly not more if you're on a wired (!) connection. Over Wi-Fi it's crap, of course.
Last year I connected Samsung Blu-Ray player which supported even more formats and worked even better (faster). Now, DLNA is about as shitty a protocol as possible (really, if you get down to the tech nitty gritty, "frackin' terrible" would be a compliment) so not everything always works and codec support has some limits, but some brands (including Samsung) support some non-standard stuff like additional codecs and even SRT subtitle support. Ultimately, I hacked my BR player with "SamyGO" which allows you to use network shares directly instead of DLNA which made it even better.
I've used laptops for this purpose and have even built HTPCs, but if you take a little care about what you download, by far most things will play on a DLNA setup on modern TVs and BR players (support differs per brand). My PC is usually turned on in my office room, I download my shows and movies (usually x264 720p or 1080p in mkv format with optional srt) and play them back in the living room without any additional gadgets at all.
Then again, maybe none of your TV room playback devices support DLNA or your computer isn't always-on, both will ruin this setup