use AHCI... Otherwise your system will be too slow...
on AHCI the burst rate of xfer between SATA Hdd can reach 100 MBps and averages around 50 - 60 MBps ... on IDE emulation ... data xfer will not cross 50 MBps... my experience with AMD 780g...

enable AHCI
enable SATA Native ports...
2 devices will be detected as IDE and rest as SATA...
if you enable IDE Emulation then
4 Devices as IDE and 2 as SATA..

you problem with 33% expanding is not the fault of your Hdd's AHCI mode but
with your DVD Drive + Media they suck man....

Thats why i always install vista and XP by pendive ....

if you need help with installing vista / XP with Pendrive ...
post here / Pm me i will post a guide for the same...

peace
raj