The most common modifications for the Sega Dreamcast are optical drive emulators, which negate the need for BIOS replacements, though I can still install these for you. I don't really carry this particular blank ROM chip for flashing; you'd have to provide the preflashed BIOS IC. Other mods include upgrading the controller board components and making some changes to be able to use common non-rechargeable cell batteries for keeping the clock and date settings.
When it comes to optical drive emulators, your best bang for buck is a v5.15 or v5.20 GDemu, though the Terraonion MODE offers more features and a far sleeker user interface.
The controller board kits generally come with a resettable fuse, capacitor, a non-rechargeable CR2032 battery, a cell battery holder for easy battery exchanges, and a diode like the 1N4142 to block the charging current from reaching the now non-rechargeable battery. The kits are often sent in with the console to have them installed along with other modifications, but we can source these components for you on request.
People like to upgrade the fans on these systems as well, like the Noctua fan. These can be installed on request, but we don't carry the fans as stock.
The system has a variety of aftermarket power supplies available, like the PicoPSU, which is a small form factor power supply that can be installed in place of the original power supply. This can be a good option for people, though I've had extremely bad experiences with cheap Chinese units and low-quality power bricks. Due to bad past experiences, we only offer a warranty on systems with stock supplies and can recap these for you. When testing these systems, we will power them up with a stock supply then install your aftermarket supply before dispatch. Only buy reputable Pico supplies! We won't even attempt to turn your system on with an aftermarket supply and power brick. This is just to cover us, as we've had to replace fried mainboards and even a DCDigital Kit in the past due to a bad Pico/power brick combination.
Speaking of which, the is one hell of a kit.
Check out the features on that link... It's even better than the first revision and it beats the hell out of any analog to digital conversions.
We can install these for you for $199 + return post.
Please note: the Dreamcast comes in 2 main flavors. The VA0 systems use a 2-pin fan + thermal sensor with a 5V logic-driven GD-ROM (disc) drive, and the VA1 system uses a 3-pin fan with an RPM sensor along with a 3.3V logic-driven GD-ROM drive. Although they use the same ribbon cable connected to the mainboard, the pinouts differ. The DCdigital is compatible with both models, but the GD-EMU is only compatible with VA1 systems' 3.3V logic levels unless you perform a further modification. We can perform this modification for an additional $80. However, the MODE suits both models straight out of the box.