Connecting a sub to amp pre-amp outs?

I know this is a painfully ignorant question for most of you guys, but bear with me. I have never had a sub before so... There is no sub out on my integrated amp, but I do have a pair of pre-amp out jacks. Can I connect these directly to the low level inputs (L and R) on my powered sub? The sub manual says I can do that, but my Arcam amp's manual doesn't say anything about that--in fact, the manual more or less says that the only time I would need the pre-amp outs is to add a power amp for bi-amping. Right now I am using the second set of speaker binding posts on the amp to run regular speaker cable to the high level inputs on the sub. What will I gain/lose if I can go from the pre-amp outs on the amp to the low level inputs on the sub?