Here's the Dreamcast specs:

http://www.cyberiapc.com/vgg/sega_dreamcast.htm

If they're right then we'd have enough RAM for the overhead, but emulating a 128-bit 200Mhz CPU on a 32-bit 333-Mhz CPU is pretty much impossible. Even at the same CPU architecture it would be nearly impossible, when you throw in a different architecture you simply don't have the CPU cycles available. Not to mention emulating the GPU and sound systems.

Just wanted to explain it so you know that a Dreamcast emulator on the PSP will never be playable if it even happens at all. I would say to get RE on PS1 and use the PS1 EMU Sony built for us