All the reviews I'm seeing here are for overclocked cards.

Is there a card that can be undervolted that also has a quiet cooler?

I'm looking to replace my old (undervolted) 9800GT with a card that supports folding...

Any card can be undervolted with a BIOS mod with NiBiTor. If you're looking to do things properly this would be the way to do it. Undervolting isn't something the mainstream is interested in so don't expect to see much material on this mod. I've done it before on a number of cards including on some older cards setting up separate 2D/3D voltages although this hardware functionality was removed from Geforce 7 onwards. With modern cards it is only a single voltage that runs all of the time which you can change.

On the 7850 I used to have, I was able to undervolt -0.38(i couldnt undervolt more)v while overclocking 22% using Asus gpu tweak... but I think nvidia cards are voltage locked in BIOS.

There are also some software utilities for NVIDIA cards offered by some AIB partners like MSI afterburner so the ATI vs NVIDIA situation is the same. I'd still go for the BIOS route as it foregoes having to run the software, especially because these kind of programs typically have obscure interfaces, not fitting in with any kind of standard, written in Chinglish and made to use 25Mb of RAM all of the time.

fyi - MSI Afterburner is based on Rivatuner. So, more likely Ruglish than Chinglish.

I most definitely never thought of the ram footprint of these programs...

As much as the interface sucks, I actually like asus gpu tweak, because you can bind videocard profiles to hotkey combinations. I have a low power profile, a reference profile, and a 1050mhz/5000mhz profile on ctrl alt 1 2 3