using Velodyne sub in 2-channel setup?

I want to use pure diect mode on Marantz receiver because sound quality is better than stereo. If I run L/R preouts to sub in, then sub out to power amp to speakers using sub x-over, will I lose signal stregth or sound quality? Should my better interconnects be used in front of sub or in front of amp? I was thinking amp.
The best sound you will get is going from your speaker outputs on the amp to the speaker inputs on the sub.
You should use a second set of speaker cables to do this.
the velodyne dls is a powered sub. If I am looking at it correctly, it has rca's IN L/R and OUT L/R. Then it has L/R speaker terminals. I'm not sure I follow Zman. How would I use speaker hookups to sub and still get power to my floor speakers from amp. I am using rebuilt H/K 16a to power focal 918's.
What Zman was trying to say was use the Velodyne as a center speaker . use the hi level inputs and dont run the Velodyne's output. Cross the Velodyne lo pass as low as you can for those speakers.
What Zman is describing is the way I have my sub hooked up. A second set of speaker cables is hooked to the same speaker terminals as the main speakers. It sounds all wrong, but the input impedance through the sub's speaker (high level) inputs is high enough that it isn't a problem. Then, as Lewhite says, set a low frequency on the sub's crossover.
so if i use high level inputs, the sub will still use the built in amp? I will end up with 2 sets of speaker leads coming out of my power amp? (parallel)
If I use the high level input, will the crossover still filter out low frequency from other speakers?
I finally hooked up the Velodyne using the high level speaker inputs. I had to turn the volume way down on the sub and toy with the crossover a bit. Seems to work well.
Has anyone else noticed that the bass seems less defined hooked up with the high level inputs?
That's why I use the speaker inputs on the sub.
Zman. I used the digital out on an old cd player for a while. I listened in stereo which enabled the sub to play also. Now that I upgraded to the Sony5400, I use ICs and prefer the "pure direct" mode. The sub is disabled in PD so I followed your advice hooking up the sub with speaker leads from my amp. The signal seems stonger as I had to turn down my sub volume...but less defined.
Maybe the sound difference is between using digital/ICs?
I was just curious if this was the norm? I am very pleased with the 5400, I have settled on a sub volume that is just strong enough to compliment the sound instead of being overkill....just seems to lack the punch; if that makes sense.
Upgrading to a good preamp made a difference throughout system...including subwoofer.