I'm told MEPIS have excellent hardware detection. Is it likely too work on my PC which uses RAID 0 on the Intel ICH8R chipset?

The RAID setup will not be going anywhere, it's a gaming machine and so will be primarily running windows.

I use Debian on my Laptop, and am aiming to move as much of my browsing and other non gaming activity to linux as possible, mostly for security reasons.

Sounds like you'll need to flub around with device_mapper/dmraid for your bios RAID.

I have a dual boot Windows XP Raid 0 bios setup; I had to set it up manually with slackware with dmraid etc, as I couldn't get Ubuntu (think it was 8.04), OpenSuse (tried 10.3 and 11.0) or even Knoppix (whatever the latest number was 3 months ago) to recognize the situation correctly and give me the options I wanted automatically. And if I was going to do it manually, slackware seemed a lot easier.
So my bet would be that Mepis won't do it without some manual tweaking. and my hardware is older too, which should have helped, I would have thought...