the roms generally consume the same amoutn of power....150watt is sufficient, depending on your other components...i.e. motherboard.
stay integrated, and preferably p3/celeron on a system w/ a 150watt psu.
aopen has the H340D case @ directron, which is a relatively nice slimeline/bookpc case that comes w/ an adequate 180watt p4 ready (12v connector) PSU....180watt on an integrated P4 board would be ample...
if u want a DVD, stick w/a combo drive...LG makes one - ricoh does as well..among others.