Change to RAID mode from AHCI mode windows 8 (64bit) for msata caching?? (Advice needed ASAP if poss. thank you)

Hi,

I have an new Alienware M17x R4 with a 256GB SSD (Added myself before a complete re-install of windows & drivers etc), 750GB HDD and 32GB mSATA.

Currently my bios is set to AHCI with the O/S (Win8 64bit) on the 256GB SSD and data stored on the 750HDD, I've been told this configuration makes the 32GB mSATA redundant and is not being used as a cache drive for the HHD (which I thought was the main point of it)  this is supposedly due to it not being configured in RAID mode, is this true? I obviously want to get the most out of my laptop and a redundant mSATA is far from ideal.

Can anyone advise me if the above is true and the mSATA is not caching for the HDD and can the configuration can be changed without doing another full re-install (I've only just finished this install...Headache! lol! ). Does the mSATA make a difference to the HDD speeds or is there a better use I can put it to (the mSATA of course)?

Any step by step instructions (in easy to understand plain English as I'm a bit of a newbie when it come to this) or point me in the direction of any instructions elsewhere?

To clarify;

my current set up is;

Bios set to AHCI

256GB SSD as C:/ for O/S and Antivirus (showing caching enabled)

750GB (7200rpm) HDD as D:/ for Data etc and game/ software installs (Showing caching enabled)

mSATA not showing in 'My computer' but shows in disc management with caching enabled.

What is the best configuration I can gain? and also the most viable way of achieving this? 

Also if I turn off caching to disc on the HDD will it automatically use the mSATA for caching? or is that just to simple?

If I change the Bios to RAID what will be the outcome, I've read the system will not boot and I may have to start again which is what I'm trying to avoid. Plus how would this affect main SSD for my O/S? Also I've read that AHCI does not allow for the SSD 'Trimming'? is this true also?

So many questions I know, but any help would be so much appreciated before I continue installing all my software and I just want to get 100% efficiency out of my rather expensive £2.5k+ laptop

Thanks in Advance!

Barrie