There's also Lil's Hobby center, at SM Mega, Trinoma and Park Square, though they have limited slections. There's also Best Toys. Both have slightly higher price points than GT.
Also, if you join the local forums (PunoyGundam, MechaPinoy, GreatToysOnline Forum), look for M1gs in the For sale section. He orders direct at competitive pricing and can get you the launch promo items and rare inclusions (like the PG 00 clear parts) etc. earlier than most stores.