Adding a sub woofer?


Running a Planar 6 to Icon Audio Ps1 Mk2 to Quicksilver Mid Monos into Klipsch RP8000F speakers. Want more low end, thinking of adding a sub. The mono blocks don't have a dedicated sub output so I was thinking about something like a PSB 250 which has both pre amp and speaker level inputs with speaker level outputs. A couple of questions.

What are the pros and cons of using the sub's preamp level inputs vs the speaker level inputs in this application?

And more importantly, right now my setup is pretty much tube analogue the whole way (and aside from the soft low end, I absolutely love the overall sound) - but does an inline sub like this do any processing, will it color the mids and highs in some way or is it just a clean pass-through in terms of sending the signal along to the speakers? 

Thanks for sharing your thoughts. 
Ryan
spotconlon
I have a very good tube untegrsted in Ayon 
and a very solid Yamaha 2100 both have active preamplifier sections , SVS, or crutchfield sells a resistor adaptor that connects directly to speaker outs on the amplifier , it is more accurate 
and better Bass control 
if you sub has speaker inputs, like rel  has it’s a very good setup .
I use this which it has a + and - per channel ,you use awg 16 wire I use Neotech and crimp bananas to one end to go into the speakers ,the other side plugs into the adaptor board and there 
you plug in rca sub cables into the board ,the other side into the sub input , it’s sounds like a lot of work ,but it’s not and only
$30 I Velcro to the back of the audio stand.
Another brand of sub you might want to look into is HSU VTF-2 MK5 or the VTF-3 MK5 HP
Adding a sub(s) is one of the most challenging things to get the sound response you want. Ideally, what millercarbon suggests is the most sensible approach to this challenge. The approach to adding multiple subs (sometimes referred to as "swarm") is ideal.
However if you are not ready to get multiple subs you can look at the various wiring techniques mentioned here. Or, you can look into integrating a sub(s) by using an active crossover with bass management capability. Those crossovers can be from reasonable in price to very expensive. My solution was getting an Outlaw ICBM crossover. Original retail was $250. Don't believe it's still in production but can be found in the used market. A crossover of this type, with sub out connection, can be connected between the pre and power amps to perform bass management as well as adjusting crossover frequency to the mains. Not the supreme setup but can make integration of a sub much easier. That's the most important thing rather that how you wire up the sub.

I also have a system with Klipsch RP8000F speakers.  I have 2 SVS SB 2000 subwoofers with these, and they sound great!  I use the pre-out to the subs from my amp as recommended by SVS.