I guess it all depends on what you are considering a complicated/fast track when it comes to that bass
Guess I can tell you what I think of a couple tracks I consider somewhat congested if you will:
On Cayin N3 EQ Off: 40 Stories by Dishwalla (All files WMA 168Kbs) at 50 (Half Volume) they are excellent at keeping the bass in character to the rest of the instruments and vocals, the crescendo 29-30 seconds into it is something I call congested and they hold up well across the frequency range.
Beck's "Missing" off Guero keeps that fine bass thump throughout the entire song while still letting his voice and other odd sounds penetrate with a nice visceral pleasure to it. Really love the way the violin strings just sway in and out of that bass line.
Floyd "Mother" off the Wall is a sheer delight on this setup, the first inhale is so crisp and clear at the beginning and decay on David's strings along with the almost hall effect are spot on.
And if you want to know if they can reproduce solid bass just listen to Bowie's Miracle Goodnight off Black Tie/White Noise will have you walking away rattling for an hour
You have any other suggestions you would like me to listen to tell me what it is and I'll see if I have it loaded