Not the brightest question about MH bulbs

[Jason McK]

Sorry about the pun, but I couldn't resist.

So I've had my PFO 2x250W 6500K + 2X100 VHO system for about a year now. I'm now thinking about replacing the bulbs. But man oh man. Everyone talks of all these bulbs. Were can I learn about then all. I do know about colour temperature and what that all means I really just want to know what types of bulbs my PFO Ballast will be able to drive and what the different manufactures offer over the others.

Thanks
Jason