Online Capacity Expansion only works by adding disks to a RAID array.  When you replace the disks one at a time, as you have done, the only option you will have with that new space (above 73GB per disk) is to create a second array across the disks.  This will be available to the OS as a second/separate "disk".  Backup data/delete array/create array with larger disks/restore data is the only way to turn a single 6x73GB array into a single 6x146GB array.  You may read about something called a "retag" which will appear to do what you want it to, but it is a dangerous operation - intended only for recovery purposes, not for array expansion - and will cause your array to become unstable.
I have a PowerEdge 2900 with a PERC 6/I controller that had 4 73 GB SAS drives set up as a RAID-5 for a C: partition.  I first replaced each of the 73 GB drives one at a time with a 146 GB SAS drive, and allowed the RAID-5 to reconstruct for each drive before replacing the next one.  Once I replaced all 4 drives I added two more 146 GB SAS drives for a total of 6 146 GB SAS drives.  After initialization, I extended the C: partition to maximize the new unallocated space.  My resultant capacity is 406 GB NTFS, which would be correct if I simply added two more 73 GB to the array.  What do I need to do to fully utilize the available drive space?  I am using the Dell SAS RAID Storage Manager.  I can of course use the PERC 6/I utility during bootup if necessary.
Replacing Drives in PERC 6/I RAID-5 with larger