Scansnap is for scanning not faxing. TWAIN, while OK, isn't really necessary although it can be helpful. Took me and Adam over a month to research MFP and I ended up with four models, before I was happy with Xerox.
PKA, I have a Scansnap. It's ONLY a scanner. TWAIN or on TWAIN makes little difference in AC. You can just as easily scan to PDF format, drag and drop files into AC charts.
I use Muratec-MFX 1430, my all in one device. Not the greatest thing on the planet, but the price is right and it meets our needs with more than adequate speed and efficiency.
The thing w/ these devices is to think really hard about what your needs will be. Keep in mind you may be wrong intitially. I got a cheap desktop all in one model that got me through the 1st 6months until the money started coming in. Then I took it home where it still resides and got the Muratec.
There are perks to being your own business owner. When something becomes "obsolete" or "breaks" you can simply take it home **hint hint** Business gets the tax break and you don't have to spend personal funds on the equipment.