well, I found the answer to my question by downloading the Spark User Manual:
"By default, the guitar signal is recorded after Amp/FX modeling. To record a dry guitar signal, use the SPARK app to bypass all Amp/FX modules."
I was curious about this because I was just looking at the newest version of Amplitube (5.0) and it looks like it has improved tremendously.
The Spark (on sale) isn't all that more expensive than many USB interfaces, so using a Spark for dual purposes like this could be a very good value and make a lot of sense for some people.
I have both Spark and Amplitude 5.01 - I use the Spark when I am away from home, for it's size it sounds excellent, at home it is in my workshop used as a blue tooth speaker
. I really like Amplitude 5.0, the new interface is far better than earlier versions (I started at version 3) and the tones are really excellent, equal or, to my ear, slightly better than BiasFX. I use an iRig Stomp I/O to control the software and as my AI with the Amplitude 5 plugin in Reaper. If you purchase either IK Multimedia Axe Solo ($299) or Stomp ($349) bundle you will get Amplitude 5. So price wise you are about the same as the Spark.
If you choose Amplitude 5.0 they are working out the kinks of the new release, the Stomp was seamless with version 4 but in 5 it is quirky - as long as I start it after a clean computer boot up it works perfectly, if I want to use Amplitude 5 after the computer has been running awhile it gets sketchy connecting to the Stomp. They are aware, and I expect an update to be released soon.
Spark advantage is an all-in-one package that sounds excellent for it's size. With the Stomp I can travel with it, foot control of the software/pedals/looper/tuner makes it easier to use the software - no mouse clicking needed and no app needed to send a dry signal to Reaper. I find it easier to play with the software while on a computer compared to using my phone, but that's me YMMV.