I am considering getting a refurbished G5 1.8 and was wondering whether I should go for the Rev. A or Rev. B model (from the specials area of the Apple store). With the Rev. B model, for $100 more I could get a 160 GB hard drive, 8 RAM slots, etc. Is the architechture, etc. of the Rev. B models improved enough to warrant getting it instead of the older model? Any advice would be appreciated.