[kubuntu] 8.04 copy dd / cp to larger partition and upgrade

Hello to all of you, this is my first post here and I hope to meet the cracks here
to find the solution for my multi OSX System.

So, my Problem is: I worked with Kubuntu 8.04 on my
Lifebook E8110, Core2duo, Intel ICH7 chipset, GMA945 Graphics and I have to
move my system. I copied with
sudo dd if=/dev/sda6 of=/dev/sdb5 from my old Samsung 640GB HDD to my other one.
/sda6 is reiserfs /sdb5 should be ext3 for mount issues.
The old /sda6 partition was about 14Gb size and the new one has 23-24GB size.

The partition table is MBR because GUID did not work for my multi-boot
(the partition table on my 'new' system is like
/sda1 win7 /sda2 MAC OSX 7.3 /sda5 Kubuntu 8.04 reiserfs
/sda6 swap /sda7 ext3 Ubuntu 12.04 /sda9 swap2

Now the problem is the partition size is still 13,4 GB even if I copy to 23 GB partition.
And I tried a lot to enlarge it - all the partition managers in Kubuntu 8.04 / 11.10 did
not work, tried to make it smaller and larger does not work.

So I asked a housemate how to copy only the files, not the whole partition...

sudo cp /dev/sda6 /dev/sdb5 was the answer, but same same - the partition is 13.4 GB

So, I need some help how to 'enlarge' the partition manually.