Does anyone have a good suggestion of a free bass amp simulator plugin?  Trying to get a reasonable bass sound, but with the amp sim I have the bass is barely audible.  I may be missing something within Sonar itself (didn't see much in TH3 to help, unless again I'm missing something).
 
Does anyone have any suggestions?

Hi Kevin, here's a few you can test out:
 
GK Amplification 2 LE: https://shop.audified.com/products/live-guitar-and-bass-bundle-le?variant=10324859783 
 
Ignite Amps: http://www.igniteamps.com/en/audio-plug-ins (SHB-1)
 
Bass Grinder:  http://www.vst4free.com/free_vst.php?id=2082
 
Ample Bass P lite: http://www.vst4free.com/free_vst.php?plugin=ABPL_II&id=2505
 
IK's Amplitube 4 also has a free one, but I think you'll need to install the Custom Shop software first in order to get the plugins. 

Thanks, I will give those a go :)

Don't forget Audiefex GK Amplification 2. They have a nice demo. All the Gallien-Krueger plus cabs and mics.

Oops!! Sorry, you already were told. BTW, There is a 64 bit version too.

Currently I use Waves JPP bass. However before that I used a combination of the built-in Sonitus EQ and the free Voxengo valve amp simulation. There's plenty of options in the amp drive, bias, etc. That worked well and I'd even consider going back to it.

Mesh
Hi Kevin, here's a few you can test out:
 
GK Amplification 2 LE: https://shop.audified.com/products/live-guitar-and-bass-bundle-le?variant=10324859783 
 
Ignite Amps: http://www.igniteamps.com/en/audio-plug-ins (SHB-1)
 
Bass Grinder:  http://www.vst4free.com/free_vst.php?id=2082
 
Ample Bass P lite: http://www.vst4free.com/free_vst.php?plugin=ABPL_II&id=2505
 
IK's Amplitube 4 also has a free one, but I think you'll need to install the Custom Shop software first in order to get the plugins. 

Thanks for that Gallien-Krueger link!  Didn't know about that one...
 
I have a couple of Ample basses, including the Stingray 5 "Metal Ray", and wow it sure has a whole new attitude!!!  And it even give the Ample Bass P Lite a whole new level of thump!
 
Playing a metal riff on the B string, with the GK preset on "Monster bass", and Wowza!!! 

Let's not forget Overloud's Mark Studio 2. It's become my go-to bass amp sim.

dlesaux
Let's not forget Overloud's Mark Studio 2. It's become my go-to bass amp sim.

Not free though which was one of the OP's requirements. If your buying then the Ampeg 2 stuff for Amplitube is also worth looking at.

Yeah, it's freebies for now.  I'd like to save up and get the full whack of Guitar Rig at some point, which I've tried on a friend's PC and I think is awesome.