PCI express cards & performance

I've tried 2 different PCI express cards in a 2010 Mac Pro and have the following observations:

Boot time increases substantially... my guess it's taking longer to identify boot disks.
Disk performance via PCI express is worse than just plugging straight into a SATA slot: even with using a 6G PCIe eSata card to a RAID 0 enclosure.

Moving a PCI card from the mac to a pc & performance on the pc is much higher than that on the mac/SATA slot.

This is an expensive trial & error approach & I really don't want to spend more $'s on boards that exhibit the same problems.

Is there a decent PCI express board that will allow for improved disk (ssd) I/O performance or is there a known issue?

https://eshop.macsales.com/item/Newer Technology/MXPCIE6GS2/

maxpower esata 6g pcie 2.0 controller

http://g-technology.com/products/g-raid.cfm

g-raid 2TB to which I've voided the warranty to open up to test & compare performance of 2 OWC Mercury pro SSD's in hardware RAID 0 through PCI express eSATA against the same 2 SSD's in software RAID 0 direct attached to internal built-in SATA connectors as well as a single SSD similarly connected.

http://www.ocztechnology.com/produc...revodrive/ocz-revodrive-pci-express-ssd-.html

ocz revodrive pcie ssd

My benchmark test should be CPU bound but involves a lot of random I/O with an average of 4k units. Bottlenecks in the I/O system are easily identified by seeing the CPU utilization fall below 100%.
A RAM disk demonstrates this perfectly.
The SSD connected through built-in SATA approach shows some early latency & can't sustain 100% cpu utilization for more than 2-3 seconds.

Using the PCIe SSD Revodrive CPU utilization is very erratic, never 100%, and often falls to 10%, never more than 80-85%.
Using the MaxPower eSATA 6g PCIe controller, CPU utilization is also erratic, never over 40% when using the same SSD's, and never over 5% when using the provided Hitachi HDDs.

Also using ATTO & CRD through Windows on the Mac Pro, or Digitools through OS X, which independently verify performance of any PCI express configuration tested is poor.