WRX stuff won't interchange to the SVX, I've tried. Your friend has two options; stock replacements, or Koni inserts (w/stock springs or Ground Control coli-over set-up). Stock struts are relatively cheap via Internet dealers. He can expect to pay about $650 for the Koni inserts (which require gutting the stock struts) and another $400 for the Ground Control set-up which requires some welding.
Send your friend over to www.subaru-svx.net.
Lots of pics of peoples swaps over their. A member recently designed some performance springs (non-coil-over) for the SVX. Slight lowering and slightly increased rates.