Question

Dell XPS 8700 Window 7 Pro, 8 Gb ram, Intel i5

Answer 1

No.  It isn't a question of computer hardware specs.  Its about your recording software/DAW.

Most recording software/DAW can only use 1 audio recording device at one time.  

You can however have multiple and different devices installed and connected to 1 computer.  But again, most recording audio software will use only 1 device at 1 time.

If you need more channels with your setup, you will now need to consider a different recording interface that has as many channels as you may need.  There are many different audio recording interfaces that can suite many different setups and rigs.

Answer 2

What I do to use more then one interface is I use Reaper as a VST in StudioOne, then in Reaper use the second interface with a clean input. In turn you can use this as an instrument in StudioOne. Takes some trial and error but it works.

Answer 3

I don't think the other commenter is correct. Many DAW's, including GarageBand can record multiple channels simultaneously. So if that's the only reason to claim it isn't possible, then you should be able to connect as many interfaces as you want (within limits notwithstanding.) I haven't tried two of the same kind of interface, but have used a Presonus Audiobox iTwo with a ADC microphone simultaneously.