Virtually any DVB receiver will run your motor, and you can use either USALS or DiseqC-1.2, ie you don't "need" USALS software, but it's part of most software that runs the Twinhan. However it sounds like for you, you need to first align your system, and aligning a dish with a computer card receiver can be difficult in some respects. Most hobbiests would probably suggest using a STB for the alignment process, since you can take that out to the dish, and the signal meters are a bit faster in response, although still slow compared to analog standards.
If you MUST align your dish with a computer card, I would really recommend trying to use a program called THMOVER, which is a very simple program that will allow you to type in freq/sr , move the dish via diseqC-1.2, and see a signal meter. However you still really need to be able to see this display from the dish while you're making adjustments. Since your Twinhan is likely in a desktop computer that can't easily be moved, I think the best way to handle this problem is to use a laptop connected to your desktop by wireless network. Ie you can run a VNC server on the Twinhan desktop, and a VNC viewer on the laptop, and this will allow you to see the S/Q meter on your laptop out at the dish. I had hopes of doing this myself, however I forgot that there was a metal roof between my wireless router, and it didn't have enough range to get out to my dish unfortunately.
One thing about the Twinhan though, and that is to make sure that you have an ample power supply in your computer. I originally had a slightly underpowered power supply in my computer, and while the Twinhan worked fine as a receiver, the power supply introduced a lot of noise onto the coax, which seemed to interfere with the DiseqC signals. I could see the noise on an oscilloscope. After I upgraded my power supply, the Twinhan worked fine with DiseqC, and moved the dish fine, and switched switches fine. I've read a lot of posts suggesting that the Twinhan had problems with certain DiseqC hardware, some giving instructions for fixing the hardware, but I think the problems may all be related to noise from the computer's power supplies.