Standalone for what car? Universal, or car specific, like Hondata? Usually, a standalone will cost about 50,000 to 80,000 pesos, depending on the type... and that doesn't include the cost of installation (budget another 5k, just in case) or tuning (5k, 10k, 20k... depends on how many hours and how complicated). Sabi ni Auto_Xer (he's not here often, you can find him at Kotse.com sometimes), last installation nila nito, it took about 8-10 hours for the tuning alone. At 5k per hour, that's a lot of moolah.

I don't know any direct sellers, but most good speedshops can import and install it for you.

Unless you're running 13:1 compression on a car with direct ignition, and are running sick mods like super-lumpy cams and individual throttle bodies, a piggyback will give you nearly the same amount of power, for a much lower price.