No matter what disk types you are using you can always pair any size disk with another. The caveat there is the RAID size will always be limited by the smallest drive.
As stlcardinals mentioned, RAID 0 is useful for streaming large data sets. Typically seen in video stream/processing for temporary data. For home use, unless you are transferring files constantly and require a larger amount of IO processing than a single disk can provide RAID 0 is a perfect solution. If you don't care about data loss that is.
Higher level RAIDs say a RAID 3 or 5 the next step in the parity RAIDs, are options only if you require data availability, and want more usable space than a mirror RAID type 1, 1+0, 0+1, etc. can provide. The parity RAIDs are nice, but you take the performance hit on the writes. For home use this really isn't a problem as, home users tend to do mostly program installs and just want data availability.
If you don't mind using half the space, a mirror RAID is what I prefer to run. 300GB of data is a lot of data to worry about backups with. Knowing you run a mirrored RAID on a data set that large would be recommened. Of course if you run RAID 0, you can lose the full 600GB .
RAID 0 will not give you much for games if that is the rationale. Along with the fact that the more disks in a RAID 0, the greater the chances of failure on the array makes RAID 0 a poor choice for long term storage.