I have found incorrect information regarding adding an external multiple drive bay that requires a sata port multiplier to see one big RAID drive via eSATA in this forum and other google searches.

The EVGA x58 SLI board comes with an internal SATA port and eSATA port that is run through a JMICRON JMB362 chip.

I purchased a STARTECH  SAT3520U2ER sata drive enclosure with RAID. I had 2 x 1.5 TB segate hard drives. The enclosure supports up to 2 x 2TB drives. You can set drives up as JBOD, BIG and a couple RAID options. The device can connect via USB or eSATA with the restriction that to use some of the RAID functionality the port must provide a SATA port multiplier.
 
I was interested in getting the biggest fastest drive possible. I want a single 3TB RAID 0 drive via eSATA cable. Through trial and error I got the unit to do it.  I wanted to share how it is done.

1) The device allows you to hard configure via dipswitches the mode (BIG, JBOD, RAID) or set it so that the software can change between these. The first thing you have to do is set the dipswitches for the GUI interface to control mode of operation.
 
2) Boot the computer with the device turned off and the USB and eSATA cable connected ONLY to the enclosure.
 
3) Install the software and open the GUI from the system tray.
 
4) Power up the device and plug it in VIA USB interface. Windows will install a driver.
 
5) Through the configuration function of the gui setup the drives as a RAID-0.
 
6) Once complete go to Computer Management -> Disk Management (on Win7) and choose GPT over MBR for this device then format the 3 or 4 TB drive NTFS with whatever cluster size you desire.
 
7) After formatting is complete you have a single RAID-0 drive greater than 2TB but going through a USB connection. Uplug (safe removal) the usb connection and turn off the device.
 
8) Plug in the eSATA cable into the computer and turn the device back on. Windows will install a driver. You now have an eSATA connection.
 
8) Boot the machine and during the BIOS screen for the JMICRON controller it will dispaly the device as the total size of both drives as opposed to the size of one.

A quick update - I uninstalled the software after getting done and everything runs great. I turn the device on only when I want to back something up to it. You have to "scan for hardware changes" to pick it up. This can be done via the command C:\devcon.exe /rescan. If you don't have devcon you can download it.
 
I copied one folder containing 1,328,155,656,192 bytes from an internal SATA RAID-0 array of 3 drives (which is faster) to this device and it took 175 minutes. That's an average of 120.63 MB/sec.