Help with Caps if you can

I have purchased a used Sonic Frontiers Line 3, to replace a Sunfire Classic preamp. The line 3 sounds really good in the mids to uppers but lacks bass (seems maybe a few Hz) and also punch and focus, that is compared to the Sunfire.
I have tried replacing tubes (6922) and also a different amp, and still not as much bass.
Under the hood it appears that the output caps have been upgraded to Jensen foil in oil rated at 0.33 uf.
Could the Caps be limiting or rolling the bass?
Would replacing the caps with 0.1 uf fix this problem?
Any help would be appreciated.
Thanks Dave
Making a coupling cap smaller RAISES the filter point. It sounds to me as if that point MAY be too high already.

Anyone know what the original value is?
Jeffrey is right that going to a .1 will only make it worse. The impedance of a .33uF cap is 24,000 ohms at 20Hz. That means even with a relatively high amp input impedance of 100,000 ohms the response will be down about 2dB at 20Hz. That's quite a bit. It will be worse if the input impedance of your amp is lower.

That compares to only about - .3dB for a 2.2 uF cap.

I think your caps are too small if those are the output caps. Are you sure they aren't the caps between stages?
Go direct!
Shunt DC to the ground using diodes.
Dave, if you don't have a schematic diagram, can you determine the value of the load resistor(s) that follows the coupling caps?
I don't know what the original caps were, or the values, but the Special Edition upgrade offered by SF used MultiCap RTX polystyrene capacitors, and the SE plus upgrade currently offered through Partsconnexion uses Audio Note Silver Foil capacitors. I will be receiving a Line 3 SE any day now, and can then compare it with the Line 2 SE I currently own, relative to bass response. The Line 2 already goes pretty deep, but the bass is just not quite as tight as with my SS preamp. The bass of the Line 3 is supposed to be improved over the Line 2. It sounds like maybe someone has been experimenting on yours. You could call Chris Johnson at Partsconnexion who would know what the values were, and maybe sell you some of the Audio Note caps. Let us know what you do and how it works out.
Make the coupling caps larger and use Chris Venhaus oil-cap V-caps bypassed with smaller V-cap Teflon caps. This is the closest thing to a wire that I have heard.

Steve N
Empirical Audio
Thanks for all the help. I jacked in 1.0 uF caps making 1.33 uf and most, but not all the bass reappeared, then tried with 2.0 uf added, which was a little too much, so I think the correct value is 2.00 uF. Am wait for confirmation from Parts Connexion.
Also found that Jensen Oil caps sound a lot better the Solen poly caps
Hello 883. I would take the parts connextion's recommendations straight to the bank. Chris knows the preamp's voice inside out and backwards. That said: I am a big fan of the V-caps, I use them for couplers in my Vac monos as well as the crossovers in my Tannoy Westminsters.