long story short, i'm contemplating the proper PCIe SSD size on iMacs and nMPs. typically i would put my OS & apps on the internal SSD and everything else on other drives. since these new machines have SSDs which may never be replaceable but are also incredibly fast, i am wondering if i should buy more storage than i need with the thought that i should point my scratch drive to it as well (e.g., photoshop scratch). i do plan to bump up RAM a fair bit, which might reduce but not eliminate the need for scratch. my other alternative is scratch via SSD over thunderbolt. thanks for the thoughts!