FreeBSD + Disk speed

[graudeejs]

I got IDE disk (160G) and SATA150(250G) disk
Currently:
FreeBSD is on SATA disk
Torrents are downloaded to SATA disk
Files are archived on IDE disk...

I'm wondering if this setup would be better in terms of performance:
FreeBSD on IDE
Files archived on IDE
Torrents are downloaded to SATA
/usr/ports on SATA (optional)
/usr/src on SATA (optional)
/tmp on SATA (optional)

I use my pc for desktop.
I download torrents a lot (at high speed)...
and i think once FreeBSD is loaded disk usage for it is very minimal
That;s why i'm thinking if putting FreeBSD on slower disk, and running most things that needs speed on faster disk would increase performance...

Bough disks are and will be encrypted

Filesystem         Size    Used   Avail Capacity  Mounted on
/dev/ad4s1a        496M     51M    405M    11%    /
devfs              1.0K    1.0K      0B   100%    /dev
/dev/ad4s2.elig    5.9G    449M    5.0G     8%    /home
/dev/ad4s2.elif     12G     32K     11G     0%    /tmp
/dev/ad4s2.elid    9.8G    3.6G    5.5G    40%    /usr
/dev/ad4s2.elie    1.0G    150M    777M    16%    /var
/dev/ad4s3.elid    200G     48G    136G    26%    /home/Files
/dev/ad0s1d.eli    146G     64G     71G    48%    /home/Archive

ad4 is SATA
ad0 is IDE
atm