My macintosh has its stock 20GB 7200rpm ATA/100 drive plus a 9.1GB 10,000rpm Ultra-160 SCSI drive (Seagate Cheetah). I don't notice a huge difference in performance... most of the time. There are clear exceptions though, and I feel they are significant. Specifically, it matters where I keep huge bitmaps (like 4000 x 4000 textures and Photoshop scratch files) and and also where I store thousands of small files that might need batch processing (like my website images and html pages). The SCSI drive clearly outperforms the ATA drive in extreme drive-based operations. Huge texture files open in photoshop and poser much faster from the SCSI drive, and doing batch operations on many small files (e.g. resizing website thumbnails) is also considerably quicker (due to the high-rpm and low seek time of the cheetah). This is not purely an ATA-vs-SCSI issue though, you can get very fast ATA drives that rival the midrange SCSI offerings. For the big picture, I agree with the advice above from ryamka: put your money into getting the best processor you can, then into RAM, and upgrade the drive if you have money to burn after that. The drive will help with speed, but it will help you the least of these 3 things. -Adam