I have tested a Novatel Wireless XU870 express card with a usb → expresscard cable connected to rb411u and works great and have external antenna connector.
I’m looking at the Option GTM382 W, although I don’t need the voice and GPS part …
Trying to find the same kind at Sierra, but it seems there is a lot of sub-version that are not on their website.
I like the Sierra Wireless MC8790 miniPCI-cards because they have u.Fl.-connectors for external umts-antenna. The MC8775 is similar but has only one (usable) serial modem channel, so you can’t read signal quality or other settings while being connected via ppp over 3G/GPRS.
If you don’t need an external antenna so give the Huawei K3520/Vodafone E169-USB-Stick a try.
Haven’t seen any 8791s, but the only difference between 8790 and 8792 seems to be the UMTS frequency bands it supports.
I’m in Europe and I’m using the 8790V. It’s a good card, connects on 3G almost constantly and claims to have a built in GPS, but I haven’t figured out how to use that in MT yet.