Value: £10 - £35, depending on condition, and inclusion of box or games, etc.
Mega CD / Sega CD
Specifications: CPU: 16-bit Motorola 68000 @ 12.5-MHz. This runs in combination with the Mega Drive's own 7.67 MHz 68000 when running Mega CD games. Graphics: Processor - Custom ASIC. Displays 64 colours out of 512.
Resolution - 320 x 224 and 256 x 224. Hardware scaling and rotation effects. Memory: Program RAM: 4 Mbit. Word Ram: 2 Mbit, used as a bridge for the two processors. PCM samples: 512 kbit.
CD-ROM data cache: 128 kbit. 64 kbit Internal Backup RAM (for storing saved games, scores, etc. for CD games) Media: CD
Value: £35 - £50. Fairly common, but often fairly tatty.
Buy Sega Genesis consoles
Buy Sega CD consoles
Sega Mega Drive II (Genesis 2), Mega CD II and 32X
Specifications: CPU: 2x SH2 32-bit RISC processors @ 23.011 MHz, approx 20 MIPS each. ROM (BIOS): 3 Kb. Graphics: Color depth - 32,768 colors on screen at standard Mega Drive/Genesis resolution. Mega Drive / Genesis and 32X graphics can be merged. Memory: 256KB program RAM and two 128KB framebuffers. Audio: Stereo 10-bit PWM (Pulse Width Modulation) mixing with Mega Drive/Genesis sound for a total of 12 audio channels of varying capability, 20 with the addition of a Mega-CD/Sega CD. Media: Cartridge - basically the same as the Mega Drive/Genesis.
Value: £50 - £150.
Depends on condition, whether boxed, and bundled games. Demand varies a lot for these too, affecting end prices greatly. Make sure all video leads are included, as these are extremely hard to find separately.