Any brake packages that directly bolt onto a WRX will generally bolt directly onto a Liberty, though you may need an adapter for rear caliper packages.
I just recently scored myself a full set of 4-piston MY06 WRX calipers (including 2-piston rears) at a reasonable price off eBay, so I'll be whacking those onto my Liberty 2.5i within the next few days once I get some spare time.

Once I see a cheap set of Brembos with 5x100 PCD discs off an earlier STi, I'll be grabbing those assuming a reasonable price can be bid. EDIT: And wouldn't you know a relatively cheap set of Brembo's came up on eBay, so now I'm abandoning the WRX caliper idea.