Since I haven't had cable for about 7 or 8 years, I'm overdue for an upgrade of my media center. Right now what I've got is slightly better than just using cable, but is better than cable.
For starters, I've got a 55" Samsung LED, along with an Xbox and Mac Mini. The Samsung is great and doesn't really need an upgrade since it's a flat screen, super light, decent picture quality, and doesn't heat the room up. I use the Xbox obviously for playing games, but it's also great for streaming content like YouTube and some sports, as well as playing DVDs / BluRays (which are now few and far between). The Mac Mini is my way to get to Netflix, Disney+, and more streaming like NFL, Formula 1, Basketball etc.
Connected to the Mac Mini I've got an old Western Digital 1TB external HDD which I use to store all of my TV shows and movies that I've downloaded over the years. I'd say I have a little under 100 movies and TV shows, near max capacity of the drive. Definitely room for upgrades here for space and speed considerations. Connecting over USB 2.0 is super slow especially if I want to do other things with the Mac while watching a video, like downloading other videos etc. Playing TV or movies all run through VLC or QuickTime, which seems like enough to handle whichever format I find the media in.
All of the media center devices are connected to the wireless router, so I do take a speed hit, even though they're right next to it. I've got Cox Gigabit Internet so it's not bad at all and shouldn't have to ever worry about speed. The Panoramic WiFi router works really well and takes a lot of the config out of my hands.
Rounding it out are a wireless keyboard and mouse, which are so much better than an overpowered remote. There are some cool solutions for minimizing remote control to a smaller keypad but I don't see myself doing that anytime soon.
Eventually, I'd like to connect all of this over a home LAN and access it any room of the house. I'd love to be able to plug in to the wall and have a TV online and be able to access my personal media catalog. I'll need to buy some networking gear like a good switch.
I think the first couple of upgrades would be to get a QNAP storage server, offering so much more store and speed, as well as more control. Also, it would be nice to upgrade the PC away from a Mac mini and something a little more low power and less maintenance, maybe like a Raspberry Pi.