Onboard Intel RAID (x48) vs. PROMISE SuperTrak EX8350

So I just purchased a PROMISE SuperTrak EX8350 (still waiting for it to show up). I’m planning on revamping my storage in my computer and I am planning on how I am going to set it all up.

Here’s what my setup will have:
Storage Related:
Asus Rampage Formula (775) – Intel X48
PROMISE SuperTrak EX8350 – PCIe 4x (will be putting it in my second PCIe 16x slot)
**All drives are 7200RPM SATA drives unless otherwise noted
7x WD 320GB
WD 1TB Caviar Black
Seagate 500GB
150GB Raptor (10k rpm)
74GB Raptor (10k rpm) (16MB)
Liteon 20x DVD RW drive

Non Storage Related:
4x 2GB GSkill DDR2 800
nVidia 280 GTX
PC P&C 610w PSU
Antec TP430w for some of the HDDs
Lian Li V2000B

Here’s what I’m wondering. I read a review on this card on xbit labs and it said it was a bit slow when doing parallel writes or reads (can’t remember which). I currently have a cheap PCI software RAID card (not using RAID with it) that the Promise will be replacing.
The transfer speed when copying files to it is extremely low (something around 20MB/s). I know this is because the card is just crap, that’s why I’m replacing it. I had setup a RAID 5 array on it when I first got it and it was even slower (like 10MB/s). I also setup an array on the onboard controller and it was much faster. The onboard is also MUCH faster when running single drives.
I know that this card should be faster when running a RAID array compared to my onboard, but I’m wondering is which one will be faster and how much faster when running single drives (i.e. running one or both of my raptors off of it vs. running them using the onboard).

Here’s what I was thinking of doing:
On the PROMISE SuperTrak EX8350:
6x WD 320GB drives running in RAID 5

Onboard:
150GB Raptor
74GB Raptor
SATA DVD RW
1x WD 320GB
500GB Seagate
1TB Caviar Black.

Would I be better off running my Raptors on the RAID controller? (150GB for OS, Games and Apps; 74GB for page file and overflow games).

Thanks,
Gary

Currently I have Win7 installed on my Raid 5 and it's way fast. It does get a little complicated getting it to install windows onto the raid because you have to load the drivers for the raid card but it think it's well worth it. Looks like that raid card has 8 slots so you could see about setting up a Raid 5 with the 6 320's and then run the raptors in a separate Raid 0. Not sure if the card could handle running both raids (i'm sure it could) but you could try also run a Raid 5 off the card and then do the Raid 0 with your raptors off the mobo. Either way I'd make sure you run the raptors in a raid to make sure you take advantage of their full potential. let me know if you're interested in some speed comparisons of a single drive vs my Areca Controller with a
Raid 5.