For an old motherboard, that's not a bad idea.
I'd posted a lot here recently in Mem & Storage or in Operating Systems about my obsessive Windows Home Server 2011 "hardware upgrade" project. this was a system based on an ASUS 680i motherboard with NVidia chipset and nFarce controller. nForce never adhered completely to the AHCI spec, even though it was a reasonably good to damn-good onboard SATA-II controller.
I picked up two StarTech PEXSAT34RH controller cards for use in the PCI-E slots. These are SATA-III hardware controllers, four ports each with a port-multiplier capability, also capable of RAID0, 1 and 1+0 or 10. You never have to enter the BIOS for these cards: by default, all the ports conform to AHCI 1.x-whatever. In a PCI-E 2.0 slot, they'd provide maximum performance at SATA-III, or at least "average" for that spec. But the 680i board provides PCI-E 1.x. Still, benchmarks show something in sequential reads exceeding 350 or 400 MB/s.
There are all sorts of PCI_E controller options. the StarTech card uses the Marvell 9230 chip. ASUS, Rosewill and a few other manufacturers provide similar cards with the same or similar controller. The key thing to remember: You don't need a "Marvell" driver for the card. It installs the native Windows MSAHCI drivers and works great that way.
As to drives that require GPT over MBR to format beyond 2TB. Depends somewhat on the OS. In WHS 2011, the OS alone will require a second storage volume on the same disk. But with Acronis True Image 2014 Premium, you could supposedly create a single volume for the entire 4TB partition. And of course, in Windows 7, you should be able to do it without any such software assistance. Either way, as long as you create GPT partitions.
One more here. The Marvell 9230 chip provides for an SSD caching solution similar to Intel's ISRT, but there's no limit on the size of the SSD you can use. I think it's called "Hyper-Duo" or something like that.
These controllers are about $75 each, and similar by other makers are even less.