Sorry, but this whole area of filters, cross overs and such is SO new to me (i feel pretty dumb, actually, as I'm finding, if you do some research that Bass is a MUCH more complex issue than just throwing down a boom box in the corner), ie, items from Marchand, Behringer Equalizer, Outlaw Audio's ICBM units, etc.

I just got into high end audio a little less than a yr ago (my bud gave the '
first 'free' injection)

For now i will stick with 2 channel, but will probably buy the Denon 3803 multichannel receiver (7.1 x 110 watts/channel) as I also have a pair of Mission 731pro bookshelf speakers i might use as the rear for HT
(i will probably go that route is a few months).
I just don't want to sacrifice sound from 2 channel, if i go this route.

ROOM DIMENSIONS:
-9 ft ceilings, 13 ft wide x 35 ft** deep
**actually the sofa end the living room at 15 feet but continues back into the kitchen, hence the longer measurement of 35 feet as stated.

MUSIC: 50% music (rock/jazz/blues/some classical), the remainder is HT
I can't play at ear splitting volume levels as I (for now) just rent.

EQUIPMENT:
-Unico INTEGRATED hybrid tube/ss amp (80 watts/2 channel) by Unison Research in Italy (modded by chris johnson of Parts Connexion).
-Sony 999es sacd/dvd player modded by audience av
-Devore Fidelity (ported) Gibbon 8 floor speakers (35-25 hz)
I also have an integrated (older) NAD 710 (20 watts/2 channel)amp/receiver.

Just recently I had Chris (parts connexion) put in 2 full range (l/r) preamp outputs to drive pair of subs (rava or SE edition) in the Unico integrated amp.

will any of the aftermarket accessories work (marchand, icbm, behringer, etc)

I recall Chris Johnson emailing me noting that using a high pass filter in my system is difficult (like the one HSU makes, as I was considering the VTF-3) "Most subs have a low pass....so, a full-range output is fine.....but you have an integrated amp, it's difficult to bandwidth limit the amp...to give it a high-pass filter, really, you need a separate preamp, amp and outboard cross-over then.....".

Basically I want to get the most versatile system for my room and have great bass I can control fully and not kill my speakers, but am confused over if the sub I choose (probably Adire Audio's Rava) will work or not (esp if I go the denon 3803 multichannel receiver route or if i buy some of the aftermarket items/ marchand/outlaw's icbm/behringer bass equalizer.

Any suggestions are MOST appreciated, esp if you can help direct me through this nebulous area.

my first question is what exactly are you asking/trying to find out? then perhaps i can delve into answering it. also, denon is replacing the 3803 with the 3805, i think it may already be released...

You might investigate this thread, although it requires 2 subwoofers as if you need to buy more stuff:

http://ubb.outlawaudio.com/ubb/Forum4/HTML/000250.html

Basically can I get better bass control by using one of these units on 2 channel as well as on a multichannel receiver?

I understand that because I have an integrated amp, (unico) it proposes limitations as to aftermarket bass mgmt issues.

multichannel meaning dvd-a or sacd, i would say yes. dolby digital, dts, etc. i would say no. it really depends on how much tunability you desire and how much you can get from your equipment that is upstream from the sub (or icbm if using it). if you listen to a lot of dvd-a or sacd from a dvd player that has poor bass management or none at all then the icbm is nice; if you have a lot of options on your dvd player it is not going to do as much. as for me, i dont use dvd-a or sacd (though they are much nicer than regular cds) because there isnt too much out that i happen to like, but if thats your plan and the above about the dvd player is accurate for you then get an icbm.