How much RAM can I have with an OCed Q6600

Hi

I have built my last 4 PCs, but with built systems being so cheap, I don't think its worth the bother to build one, apart from the fact that you can build it with the parts you want and not compromise.

However that is the dilema I face. I have the opportunity to buy an already built OC'ed Q6600 (not sure what it is OC'ed to though). It comes with 2Gb PC8000 Corsair XMS ram and a single 150Gb Raptor drive. The motherboard is an Asus P5K and the CPU cooler is a Titan Amanda beast. I would rather have 4Gb although I understand that my 32bit XP pro OS will only see just over 3Gb as other peripherals require some memory addresses. I would also like to have a Raptor RAID array. The manufacturer tells me that I can only have 2Gb and a single Raptor if i want them to overclock.

My questions are

1. Does this sound reasonable or should I push for 4Gb and/or RAID?
2. Also does anybody have any experience of the Titan Amanda cooler? I did see a review on this site which compared I think upto 32 coolers including the Tuniq Tower and teh Thermaltake Big Typhoon, but i can't find it anymore.
3. Should I buy components and build one or buy already built?

Please could you advise

Rgds

Martin