^yeah, the ArtUSB and the Alto are both USB "interfaces". You don't need em both. The art wont work at the same time as the Alto via USB. The Art also doesn't have line outs, so you can't connect it to the mixer. What kind of recording are you looking to do? Vocals? and instruments?
I'm always unsure about USB mixers, because none of the specs I see ever seem to elaborate on how many individual tracks the mixer will record at once. when USB mixers first hit the scene, I think the usb connection just picked up the master 2-track bus. The point of multitrack recording is to get each mic or sound on its own track so you can mix after you've tracked- so an 8 channel usb mixer that combines all the channels before it hits the computer is pretty worthless. Some (or all?) of the newer usb mixers will put each channel as a separate track (or so I hear), but none of the specs I see seem to really elaborate. Just gotta make sure you do your homework on that.
If you just need to do one or two channels at a time, you can do something like the Art you listed, or one of the other nicer two channel usb interfaces like maybe an
MAudio FastTrack Pro or a PreSonus Firebox if you have Firewire. If you need more channels, look at an interface like the FireStudio or Motu 8Pre or one of the many others. **Edit- I just reread and you said you already bought these- is returning anything an option?**
The Art Tube MP wont provide much of a benifit either- the alto already has Pres in it. You could connect the ouput to one of the non-preamp channels on the Alto.
If you can give some more specifics on what and how you want to record, we can get more specific.
