RAID, Adding to exsting RAID???

I have a RAID0 at the moment, its is now too small.

It consists of 2 drives on an IDE RAID Card
I would like to know can I add 1 or 2 more drives to the RAID with out affecting the Partitions already on there.

the plan is to get just 1 more drive to make the RAID good for another year or so.

Please help me answer these question before I buy -
1. Can I add to an existing RAID Set (With partition, must be intact after procegure)
2. Increase the partition to consume all the avalible space on either 3 or 4 drives on the RAID

Thank You

Code Junkie