Currently I do not have a powered sub but I have an old passive sub from a HTIB. Is there any way to hook it up to the 1070?

You could connect it to the left and right channels. Without know what your passive sub looks like, I'd suggest that you should at least be able to run a separate pair of cables from the left and right binding posts. If the passive sub happened to have speaker inputs and outputs, you might also put it in series with the mains (run speaker wire from the 1070 to the sub and from the sub to the speakers). In either case, you'd need to set the 1070's mains to large and disable the subwoofer under the speaker setup menu. Do you have any details on the sub or the HTiB set it came from?

Here is the info from the back:
SW-06DV
Maximum Input Power 80W
Impedance 6 ohms

Here ya go:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=300-784

Make it powered for $50.

That's actually an even better idea - it pulls the load off of the 1070's amp so it can focus its attention on driving your mains, and gives you proper bass management upstream of the sub so that it gets only the frequency range it is designed to operate with.

i was hoping there was a mode where one of the channels would have just a low pass xover on it.

i have an old car stereo amp and an ac/dc convertor that i'll hook up instead. thanks for the suggestions though.

I recently picked up a powered sub, Axiom EP350, but all i had was a rca cable from an old car stereo install. will i notice a difference with a higher quality cable?

That RCA cable should work fine for a sub.