Best way to connect to internet

I currently have a 6 channel ISDN connection to the internet. For various
reasons, this is fairly trouble prone - apparently the multi-channel
bundling doesn't want to play nice all the time once you get over 2
channels.

My ISP has just informed me that he will have his CLEC certification in
the near future, so I can transfer my whole phone + data connection to
him.

I have the following setup:

ISDN/PRI coming in, 23 channels into an Adtran Atlas 550. The Atlas
splits out 8 ISDN BRI channels for data and fax, and then feeds a T1 to
our phone PBX.

I also have 2 additional ISDN PRI connections in the Atlas that I can use
for data/internet.

Here's what I would like to do:

plug one of the open ISDN/PRIs directly into my router (a linux box) and use it
for data.

Plug the other open ISDN/PRI into my fax server.

Use the Adtran to route as required. (The Atlas 500 can do magic - it can
make a single incoming PRI look like three or four, or break out BRI or
even POTS lines.)

Is there an ISDN/PRI (T1) PCI card that can be used to establish an
internet connection? I'm not looking for something like the Eicon Diva
Servers; they break out the PRI into 23 channels. I'm looking for
something like a network card that will use whatever bandwith the Atlas
allocates and run with it.

Also, is there an ISDN/PRI card with only 2 DSP modems (I only need 2 fax
lines; the closest I've found is the Diva Server 8PRI with 8 modems.)

Thanks,

-Kamus