HIDs are not a good solution for high-beams.
1) HIDs take several seconds to warm-up before reaching full brightness, this makes them un-suitable for things like flashing your brights
2) HID ballasts probably won't work well with the current Subaru DRL implementation, where the DRL is simply driven at a lower voltage.
LED lights are unlikely to be able to provide sufficient brightness to act as a true high beam. Sure, you can buy an electrically compatible replacement, but it'll put out less light than the OEM bulb.