There are boards with RAID 5 in-built, but they are not too common.
If you really need RAID 5 then I suggest an add-in controller so that you
have mobo / chipset / vendor independance - protection against the scenario
of 'my mobo died, I have RAID 5 how do I get the data back problem?
RAID 10 performs better as you no-doubt know - at the expense of disc
drives. RAID 5's pitfall is write performance which is well down on RAID 10.
RAID 5 tends to cost up front, but even if you went RAID 10 you still have
data resurection issues.
www.tomshardware.com has a current review of SATA RAID controllers with PCI
E and 1 X4 controller in the list - the performance is good & they are worth
looking at.
I feel compelled to say that RAID is no substitute for backups - a big
advantge of an add-in controller is Hot Spare drives - minimising dead disc
time is *important* as you are shot if 2nd drive fails otherwise. This is
why RAID 6 is becoming more popular.
HTH