Recently I managed to get my hands on the GDEMU – an SD card reader that takes the place of the Sega Dreamcast’s optical drive. With it you can place multiple Dreamcast game images on an SD card and load whatever game you want from a simple menu system named GDmenu. I set mine up with a SanDisk Extreme Pro 128GB SDXC and was able to fit all the games I cared about. The best part is you can play 1:1 dumps of Dreamcast games instead of burning rips to CD-Rs or scouring eBay for original discs. There is a noticeable decrease in loading times as well since there are no moving parts.
In addition to the GDEMU upgrade, I also replaced the original 30mm Dreamcast fan with a 40mm Noctua NF-A4x10 5V using a 3D printed mounting kit I bought off eBay (listing is gone but you can find the files for the kit here). Supposedly the Dreamcast runs hotter with the GDEMU because the GDEMU doesn’t use the 12v rail on the PSU which causes it to spike in voltage thus creating extra heat. There are some guides on the internet for either adding a resistor to load the 12v rail or removing the regulator for 12v entirely. I decided it was simpler to add a 12v fan for load and provide additional cooling to the PSU; I put a 40mm Noctua NF-A4x20 FLX in the back blowing into the PSU. Even with 2 fans, this entire setup is nearly silent compared to a stock Dreamcast.