NUFORCE AMPS FOR PASSIVE SUBWOOFERS

Nice but not powerful enough for power hungry woofers. I would rather go for any of the class D using the 1000W Ice Power module (used by several high end brands in their loudspeakers with active subs).
Otherwise, you may consider a Crown MA-5002VZ: professional 1000W amp, good value for money, supposed to be excellent to drive subwoofers.

I totally disagree with Stereotaipei. The NuForce Ref 9 mono's put out 300W RMS into 4 ohm loads and can pass undistorted peaks of 650 Watts. And the Reference 9SE's put out 250 watts RMS at 4 ohms and can pass undistorted short-term peaks of 660 watts. Although the RMS rating is at your mimimum requirement, the NuForce amps sound much more powerful because of their extremely high peak-power delivery. Plus the simple fact is that the Ref 9SE amps produce the most controlled and articulate bass performance I have ever experienced.

My feeling is that you'd be very pleased with the bass performance of the Ref 9 and even more pleased with the 9SE due to it's exemplary bass control. A more powerful ICE amp without the same articulation and control would likely be less fulfilling, i.e., it might ultimately play a single decibel louder but would lack resolution/definition compared to the NuForce amps.

Sterotaipei- Funny you should mention ICE amp. I have one that is rated at 250Watts-8ohm/500-4ohm that is being updated with new speaker binding posts. I can't wait to try it when it returns. But I'm using it as speaker amp. I've owned a Crown bass amp before, Didn't impress me, no bass definition. Sold it. I like the fact about the Nufore amps that they are small/slim so I can hide them behind the subs, sizeways against the wall I plan.

Plato- I feel why the Nuforce amps have great bass resolution/definition because of the high damping factor(>4000) which control the woofers. Do you know what the 'extended bass' option is? Can't find it on the site.
I can buy a used pair of 9.02 right now for $1350. Good deal...?!

Ptheo, $1350 is a very good price for a pair of Ref 9.02s. I'd snap them up if I was interested.

The extended bass version doubles the input capacitance and results in the bass response being a bit more linear out to 20Hz. It gives the amp a little more weight on the very bottom but it's not a night and day deal. I think Nuforce only charged about $75 for that mod.

As I have stated in my other NuForce posts, I (and others) believe the amps sound best with the internal speaker post capacitor removed (which is a cheap, no-cost tweak). You can snip one capacitor leg just to try it and solder it back in place if you think the cap makes it sound any better.