The first thing I've noticed with Macs (mac pro's especially) is that they certainly cost more than you're average pc, especially if you want any additional components such as more ram, hard-drives or a faster processor. My question is, how many things can be upgraded or replaced in a mac with parts available from normal pc parts retailers. From my understanding, you can put non-ECC DDR RAM in a mac pro (instead of the expensive ECC stuff) and you can also put in any SATA hard-drives you want. First of all, please confirm that's true. Besides that components, what about graphics cards, optical drives and processors. For example, would it be possible to put in two socket 771 quad-core xeon's? http://pcmaniacs.com.au/product_info.php?cPath=21_30&products_id=3475 ..or an SATA DVD burner of any kind? I'm not confident in the graphics card department as you'd probably need drivers and things which wouldn't exist, so putting an Nvidia 8800 in a Mac wouldn't be possible I'm guessing. Another question, I've noticed there's only 4 hard-drive bays. Is there anyway I can put my than 4 hard-drives 'inside' the case if I ever needed to? Any and all help is much appreciated. I'm new to Macs, and I think the cost and upgradibility are the two biggest things to get over at the moment. I'm looking forward to your replies!