If you want one of the newer machines then your choices are limited - Pegasos II (G4 1000Mhz / DDR RAM / AGP slot) with MorphOS at £399, or the Micro AmigaOne (G3 800Mhz / SDRAM / Onboard Radeon 7000) with AmigaOS4 Beta at £512.
Personally I prefer the Pegasos as it has a better spec and better Amiga compatibility and is cheaper.
There's also a Coldfire board called the Dragon on the way from Elbox, but this requires an Amiga 1200 motherboard.
Look at
www.pegasosppc.com for more information on the Pegasos,
www.elbox.com for information on the Dragon, or
http://www.mai.com/products/teron%20mini.htm for more information on the MicroA1.
