I cannot agree more to this. LVM is *the* way to go for you. It is not, I repeat *not* complicated. Read the LVM2 HOWTO and you're set within a short time.
However, make sure (if you plan to use ext3) to use the -O flag when creating the fs.... see my thread on that regarding resizing ext3 (on LVM on RAID5).
Pim
Sounds like an excellent reason to use LVM. pvmove the lv extents off
the failing drives (or arrays) then add new drives. LVM is no more (and
perhaps less) complicated than regular partitions and give you some
flexibility.