IMO Maxtor quality has really gone downhill in recent years, coincidentally around the time Seagate bought them (I'm no Seagate fan either). I used to buy a lot of Maxtor drives, but no longer. Personally I prefer Western Digital and Hitachi. You can get a WD 500GB w/ 16MB cache for $104 shipped from ZipZoomFly. Much better choice, IMO.
You can do RAID 5 with 3 drives, that will give you two striped drives and a parity drive. So three 500GB drives will get you 1TB of fault-tolerant space. 5 drives might be a problem for your system depending on your mobo, case, power supply, and cooling situation.