Subwoofer: How low should I go?


My B&W 683s are rated at 38Hz - 22kHz.

I've been toying with the idea of a small subwoofer to augment the low end a bit. My apartment is pretty tiny, and in a crowded NYC building so I don't have room for a big sub and don't need or want earth shaking bass, just a little more oomph.

The sub I've been looking at is the Velodyne Microvee. It fits the bill size wise. But it's rated at 38–120 Hz.

My question is, do those numbers mean the sub covers exactly the same low end as my speakers, making it useless? Do I need to go with a lower frequency sub to hear a difference?

Thanks!
rkny
i thought the rel, and some other subs, recommended running main speakers full range and simply running the sub high pass and using the on board sub xover to dial in the subs upper frequency cut off. for small, relatively well though out monitors, like my fostex 167e-based tektons, i want to get everything they reproduce and just augment, at the lower edge, since the main's aren't digging all that deep anyway, say 60hrz or so. anyway, that is what i do and am generally pleased, though my amp situation prevents me from comparing it to this other way of doing things.
Post removed 
Rkny,
The Rel T1,T2 and T3 are very compact and may do the trick for you with some effort. The effort will be required to isolate the sub from the floor as they have downward firing woofers. I have a T2 and it works quite well with my Piega P2 LTD monitors. I do not have the same concerns as you though as I live in a single family home.
As for the hookup, there are three wires on one end of the Neutrik Connector. Two go to the left speaker terminals and the third goes to the positive right terminal. I suspect that your salesperson may not be too familiar with hooking up that particular type of sub cable ???
If at all possible, maybe your dealer can let you borrow a demo and this would enable you to get a better grasp of whether you may be able to isolate it from your neighbours ears and preserve your safety...LOL
Either way, the REL is definitely worth an audition.
I was never a fan of subs in two channel environment but I am certainly a believer now.
I hope this helps.
Thanks, BJ.
If he were to go with a down-firing woofer: he could always park it on a nice, flat slab of granite. Easy to find, and fairly non-resonant.
To help you isolate the sub from the floor use cheap "Subdude" platform from Auralex. About $60.

Cheers