HTPC hardware

[brad]

I am trying to put together (cheaply and with the help of Christmas) an
HTPC box that will run MythTV as well as many other multimedia apps. 
Basically I am starting with the MB and CPU and had a couple of
questions.  I want to run IDE RAID so that read/write speeds are
better.  Is there a difference between a MB with an onboard RAID
controller and a PCI RAID controller?  Is the PCI bus going to slow it
down?  Also, is there a difference in how Linux handles/supports the two
choices.   It seems like I have a lot more options if I go with the pci
card instead of onboard.  I don't want software RAID because I have read
that this slows down the cpu.

TIA,

Brad