I've installed HID (Xenon) kits to replace my halogen lights, and the lights themselves can't get up to full brightness. They turn bright for a moment, then blue out. Is there a bigger alternator available? Or can i add some kind of amplifier to my charging system to boost wattage and amperage?

Did your kit came with the ballasts?
It seems like your ballasts (if you have them) might need to be rewired
Never heard of a car needing bigger alt to power hid

Yes, it came with ballasts. they are 35W wired straight to my battery. if i flip the switch from headlights to marker lights and back, they come on twice as bright then dim out. When the high beam is on it doesn't get as bright as it should. How would they be rewired?

Do you have drl on your ET?
Here we need to add a relay to override this component otherwise not enough juice is sent to ballast and might brake them after a few run without the relay
I would try with other ballasts imo

Yes, my car runs the high beam HID for a DRL. I added a set of relays to my lights to power them straight from the battery because they couldn't pull enough power through the stock wires. I swapped ballasts after I over worked one of them before i realized I needed extra relays. Where can i get different ballasts?