Connecting a subwoofer.....

There is, in theory, no difference between pre-outs and line-outs, so I cannot understand your question. You need to use a volume-controlled output and, if you are using a stereo source, you need to combine the two channels for the sub. Many subs actually have L and R inputs, thereby eliminating the need for a Y-connection.

So, be much more specific about what you have and what you want and, perhaps, we can help.

Kal

It sounds like you are talking about connecting the sub to a power amp or an integrated amp.

Ideally you want a sub out. Rel subs have a high level input that taps off the speaker connection right at the amp (or integrated). There may other sub manufacturers that have a similar high level input.

Xt16

Yes, I am familiar with that but I am not aware of other subs with Hi Level out. The REL seems to me the only ones I can use with a Naim Nait 5i that has no pre-out. To hook other subs up to this amp isn't possible apparently because of the lack of pre-out.

KR4,

I just mentioned the "Y" splitter as an example of possibly damaging something by messing around with this and not knowing what I am doing.That is, I don't want to make any other mistakes and regret it due to trial and error.
The question was basically asking is there any benefit/disadvantages from using either line level or pre-out when hooking up a sub that doesn't have high level outs.

Thomas, does your sub have "speaker in" and "speaker out" binding posts? If so, you can just connect speaker cables from the same binding posts you hook your speakers to on the Naim Nait... to the "speaker in" (don't worry about "speaker out") and that way have high level connection like you would with a REL.