What raid card are people using here for their mac pros? If you could get a 25% discount on the raid card, would it be worth it then? Or are there still better and cheaper alternatives?
Most people are ok with software raid... who is the raid card for????
Disk Utility is only good for 0/1/10, so if you want to run any form of parity (5/6) or nested parity (50/60), you must run a RAID card that supports the level/s you intend to run.
Another reason, is throughput. The ICH has a throughput limitation of ~660MB/s, and the Apple RAID Pro is an expensive, slow piece of junk (avoid it like the proverbial plague).
For example, those that want to run multiple SSD's in a stripe set would need to use a 6.0Gb/s RAID card in order to keep from throttling (and they don't scale as expected on the ICH either). This works, as the bandwidth is transferred over the PCIe lanes rather than the DMI connection between the ICH (what contains the SATA ports in the system).
There's other advantages to running a proper RAID card as well, mostly in regards to Online Expansion (can add capacity without data loss) and Recovery options (usually associated with redundant levels, and it's more robust than what's possible under software implementations).
I spoke to Apple support the other day and they confirm that you can do Raid 5 from the software RAID, I queried the guy and said that it can be done and it's documented.

Either there was a misunderstanding, or the person that told you this was an idiot.
Their Apple RAID Pro supports RAID 5, but it's a piece of junk, and there's better solutions out there (i.e. Areca or ATTO's products; they're even cheaper for a 4 port card that can do more).
But
Disk Utility cannot run RAID 5. Another piece of software such as SoftRAID (does support RAID 5), or the drivers that ship with a Fake RAID controller (nothing but a SATA card, and the RAID functions are software based; by far the most common way to find this),
but it's not advisable.
The reason is, software RAID is not capable of handling the write hole issue associated with parity based arrays. Even when running a UPS, as it requires a hardware solution (involves NVRAM that the system or simple SATA card does not have). You can look up the
RAID 5 wiki, as it has a definition of what the write hole is.