Vehicle comes stock with only the plastic splash guard.
Per the parts description for the metal version (PN 8622717):
XC90 Protective plate, beneath the engine, 6cyl, W0446. A protective plate beneath the engine which protects the engine, sump and gearbox from impact when driving on poor roads, such as potholed or bumpy roads. Consists of a fully covering aluminum plate which also offers protection from loose stones and stone chips.
Cost is around $300 and unless you're off-roading and you feel the need for extra protection, it seems like quite a reasonable waste of money. On top of that, it appears that you would use one or the other, not both. So you would need to do something with your old plastic guard.
If you absolutely had to have one, IPD sells theirs for $280 and I think you get free shipping on it
http://www.ipdusa.com/products/4841/109319-aluminum-skid-plate-p2-s60-s80-v70-xc70-xc90