Whether or not you run a sub inline with the fronts or out from the pre-out depends on a couple of factors. And this is not to say that you can't do both.
Generally use of an inline sub is when the sub is a passive or unpowered sub. So you need to use your receiver or amp's power to run it. In such a set-up you would do as "jazzly" did, and set the bass management to to large speakers and no sub.
Use of the sub or LFE pre-out means you are running a sub that has a built in amplifier because it's just sending out a line level signal.Now here is where a little confusion comes in. What output you get from the sub pre-out depends on how you set-up bass management.If you set for large speakers ( full dynamic range ) with a sub, then only LFE info will be sent to the sub. Meaning that you will only hear the bass your speakers are capable of producing.So check your speakers capabilities and set bass management accordingly.
Now sub bass takes alot of power to hear. This is why many recommend setting bass management so all speakers are small ( meaning a dynamic range of 80 Hz approx. and up ) with a sub. What this should do is send all sub 80 Hz bass, including any LFE, to the sub, thus relieving your receiver or amp from having to drive the low end.
Now ,of course,what you actually do will depend on the power your amps have and the effiency of your speakers. Not to mention the time involved experimenting.
