im wondering, can the daw software be configured to accept signals from 2 interfaces simultaneously?
With Cubase, you can, but you will have to use high-latency MME drivers. In Sonar, you use WDM drivers to be able to use 2 different soundcards simultaneously, but since you are accessing 2 diff. soundcards, hence 2 diff. drivers, there is no assurance that those 2 cards will be synced to one another unless you can feed s/pdif from one device to another and do a master/slave configuration, even if you are only using the analog inputs. This will assure tight sync between the 2 cards without tracks slowly drifting out of sync.
As for asio drivers, repeat my mantra: "You can only access one asio device at a time... ah-uhmmmm". Some cards, like the M-Audio Delta 1010, allow you to use 2 or more 1010's with the same asio driver but that's the extent of multiple card usage with asio. You can't use 2 different cards (with their different asio drivers) simultaneously - that is the nature of the beast.
4 tracks.. how about using the soundcard's "line in" together with the behringer fca 202?
could be, but i think there is still a problem on my theory which is also related to your suggestion. line in signals are treated as stereo to go to one track only. i dont know if its possible to send the left channel to one track and the right channel to another track.
With both Sonar and Cubase, you can assign any audio track to mono and assign either channel of a stereo signal to that track. It's the same as mono functionality provided that the left and right channel separation is very good (refer to your card's crosstalk figures).
im wondering, can the daw software be configured to accept signals from 2 interfaces simultaneously?
i think so, since you can select whatever input source you want to use per track. besides firewire devices are meant to be daisy chained. come to think of it again, i dont know if the fca202 can be treated as two mono sources on the software to be able to record from one box into two tracks.
my biggest fear here is that if i go buy 2 fca202 and still be limited to record on two tracks 
(each device treated as a stereo source only like "line in")
*if all else fails then its time to hunt for a 2nd hand m-audio firewire 1814
DAW soft can be configured to accept audio from several cards - see above.
While it's true firewire devices are meant to be daisy chained, their drivers are usually the weak point. Like I said earlier, the FCA makes no indication in the manual or website whether it can be daisy chained or not; if it had that capability, I believe Behringer would be saying so. To find out just by buying another FCA202 would be a rather expensive proposition. So far, I know that RME firewire devices can be daisy chained, but they're a bit expensive. Another device that's more within reach ($199) AND can be daisy chained, is the
Presonus Inspire 1394 - a 4-channel firewire interface.
The M-Audio is a good interface but watch out for possible incompatibilities in computers with SATA drives as it is a known problem. I know of one instance with the Firewire 410, for example, where they just couldn't get it to work on a professionally built DAW. As always, a lot of prior research is key in order to avoid the most headaches with these equipment.
