Is a Sub worth the bother?

I have a small, simple system that pretty much meets my listening needs. It's an NAD C715 (all-in-one deal) with a pair of Epos EL3 bookshelf speakers. I've been kicking around the idea of getting a cheap subwoofer with the idea that it would add a little oomph to things. This is strictly a music system, not home theater. I guess my questions are: 1) would a sub help that much or am I just limited because of the EL3s? 2) If a sub would help, would a cheap one be okay (I'm thinking along the lines of the Dayton sub 100, perhaps an Energy Take Classic 8--$100 at Costco these days). My room is roughly 12 x 20, but again, I'm not looking to bring down the house/neighborhood.

Thanks in advance for your thoughts.
I'm glad Vero made it work on his budget. Note my qualifications: IME and IMO.

I tried a more modest budget and failed. Wanted it to work - and it didn't - FOR ME. I would not try again without a Digital Room Correction/Parametric EQ device. But as Veroman's experience points out...YMMV.

By the way, it ain't market hooey. I have measured the difference before DRC and after. No mystery as to why the integration issues -and overall performance problems - were very, very audible. I suspect most hobbyists here would be stunned at how poor uncorrected in-room bass performance really is and just how badly mismatched a sub installed by ear will be. (At least my own reasonably obsessive, but sadly ineffective best effort at installation by ear.)

I'd also add that a modestly priced, by audiophile standards (+/- $600) sub like the entry level 12" models from SVS and Rythmik are awfully good. I just personally also needed the $450 Velodyne SMS-1 (RTA/X-over/PEq unit) to achieve integration I could live with.

Your experience may or may not reflect my own.

IMHO, a sub is only needed for watching movie since it needs to produce a continuous and wide bas. For listening to music, if you have a decent pair of speakers, it will beat the sub outright.

I have a 5.1 Polk system with a 10" Polk sub to watch movie and a pair of Celestion A2 to listen to music. The bass from the Celestion simply way outperforms the Polk.

I run 3 subs with my Wilson Audio Maxx3's. MX-5000's.

They are run directly off the pre-amp...NO interaction with the speakers at all, which receive a full signal from the pre-amp/amplifiers.

They are filtered waaaay down below 60hz and add a nice slam when appropriate to the music.

You don't know what you're missing! Do people ever start dancing when you play good music? No???? Hmmmmm. Wonder why not.
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If you dont run a sub, you better have some 10", 12", etc drivers in your mains if you want true live sound. The new speaker building idea is to make skinny speakers. This is for WAF, and causes us to use subs. Bring back the 12" drivers! Subs can integrate perfect, I just feel it should be placed in the center, between the 2 mains to blend (or run 2 subs, 1 behind each speakers).