The GP32 was a machine built by GamePark some years ago. It had a 133 MHz ARM9 processor, no 2D acceleration and 8 MB of RAM. It is now fairly obsolete. It uses outdated and low-capacity SMC cards and has no hardware video decoding support.
The GP2X is a system released by GamePark Holdings (GPH), a company that broke off from GamePark, who made the GP32. It has 2 200 MHz ARM9 processors, 2D acceleration by way of a blitter, MPEG4 decoding in hardware for accelerated video playback, supports MP3 and OGG audio playback in the default firmware, as well as photo and text viewing. It also sports 64 MB of RAM, as well as onboard NAND storage. It also uses the more modern and much higher-capacity SD card storage format and has numerous networking/USB features not found on the GP32. It runs a wide array of software including PC game ports, emulators (NES, GB, MegaDrive/Genesis, SNES, NeoGeo, MAME arcade emulation, Atari ST and a whole lot more.)
The XGP is a series of consoles that don't yet exist built by what remains of GamePark and whatever new employees they may have hired. The exact specs are unknown but at last notice it used mostly the same hardware as the GP2X, with the exception of ONE 200 MHz ARM9, not two, the two models have different amounts of RAM (32mb and 64mb for the XGP Mini and XGP respectively), differing screen sizes and aspect ratios, one has an analog stick and the other a segmented D-Pad. The only major upgrade is a GPU for 3D and 2D acceleration. It is unknown if these specifications will remain the same.