iMac 2.8 or 2.66?

[foothead]

Hi there. I am considering buying an iMac this summer, and am wondering if I should get the new 2.66 24" or the refurb 2.8. If I use the education discount, I can get the 2.66 for $1399, or the refurb 2.8 for $1199. Right now, I probably need the extra power of the 2.8, even though it is not much. I plan to quad boot it with OS X, windows XP, linux, and freeBSD. How much faster is the new DDR3? Are there any major differences between the two? Which do you think is the best? and also, How long do you think the refurb 2.8 will be available? thank you.