You don't need to do much with an SVT to do half-way decent in RallyX... I'd say get some new shocks (just some replacement Ford Racing ones would do quite well), 16" wheels with some cheap mud/snow tires, and remove some weight.
There's no need for serious modifications if you are doing it solely for fun!
2001 Ford Focus ZX3 - Chaos <- SOLD
2005 Ford Focus ZX3 SE - Crono
Current mods: Intake, exhaust, FSWerks Tune, SVT rear sway bar
Coming soon: SVT suspension, race header...