Which Sub with YBA Integre DT?

I'd like to get better, meaning deeper and better defined bass from my system without breaking the bank. I'd appreciate help and suggestions. My system consists of: JMLab Megane Carat speakers (2 way, 6inch mid/woofers), YBA Integre DT, MSB Link Dac III.

Would the simple addition of a sub give me better overall bass defination and depth? How would it mate with the amp, (speaker level?). If a sub is the way to go I'd appreciate suggestions and hints. Other suggestions aside from buying multi thousand dollar full range speakers would also be greatly appreciated.

Speaker level REL Storm III or Stratus III.

I found the YBA to have pretty good bass for 50 watts. What speaker cables are you using?
I use a Sunfire Architectural. Still have the sub, but not the Integre. I own the Passion, now. Worked beautifully with my Thiels, and Revel M20s. Fast, deep extension, very musical, and blended seamlessly. Carver made this sub for 2 channel lovers. Most, think of Sunfire for HT, but this baby delivers, big time, for a 2 channel set up. Don't hear much about it, unfortunately. I liked it better than the Rel, Velodyne and it stood tall against the Revel B15. peace, warren
Thanks for your replies. I don't find the bass "bad" in my system, I think it's more of a speaker issue than the amp itself. I love this amp. These 50 watts fill the entire house and we often do jazz and blues concert evenings with wine, candles and the volume pumped up to club levels. It's just that the bass lacks the imediacy, definition and extension that I know a real bass has, (my best friend was the original Holly Cole Bass man and I know what bass sounds like...). My cables are all right: Van Den Hull Cs122 I think. As far as subs go, would the Sunfire junior be worth considering? So far from the sound of it, the REL seems to be the one most suggested. I like the wood veneer too. Any thoughts on the ACI Force or any of the M&K subs?
I own a YBA Integre DT. The JM Labs are efficient speaker..would make them very suited for the YBA's. I run Totems through my YBA...I suspect I could get a better match for the amp ..but I luv my Totem and and luv the YBA sound so I'm stuck for now. My friend runs the Bryston B60 through his Totems and he luvs his Bryston. I find my amp more airier and better mids..however, his Bryston is more neutral less colored . Anyways, his Bryston integrated has variable output on rca and the YBA CANNOT!!. He runs the Totem Dreamcatcher sub through his and the sets the frequency and volume at very low and its adds little extra umph! to make it complete. Its set very low though and barely audible. The YBA's have no variable outputs so unless you want to run speaker lines through an external sub..JM Labs builds pretty nice subs..they've got a preety inexpensive sub...I think its called the CUB. Pretty sure that would do the trick as you won't need a big sub to fill in what "missing". Finally..what CD player are you using. The YBA is a very non-forgiving amp. I originally had a Rotel 971.. which again wasn't right. I now have Musical Fidelity A3. Good luck