Falling out of love with tubes

Get a tubed preamp for sure. I personally find c-j preamps a bit dark but YMMV. Also not quite sure what you mean by "going direct from my computer or tape" how are you controlling volume? Overall though a good tubed preamp won't cost you any detail, will probably add more, and will give you that more organic sound you're missing. Good luck!

By “going direct” I meant plugging the headphone out jack of my computer into the input of the SA-250 amp and using the volume control of the computer.  Also, my Denon cassette player has an output level control.  Thanks!  

I’m assuming your amp is a Sonographe SA 250. The SA 250 is getting a little old and maybe the first thing you want to do is have it looked over to see if it needs a little refurbishing.

***Will using a preamp instead of going direct from my computer or tape sweeten the sound, even if it’s the solid state CJ Sc26 preamp?

It may. Some people find that not using a preamp works best for them but I think most people prefer the sound with a preamp. In your case, if your amp sounds sterile (after you’ve had it checked out, if it’s getting old) a good tube preamp will probably help. I don’t think that the solid state SC26 will fill out the sound. The older c-j tube preamps will probably cause some loss of detail. They were made to cover up the sound of harsh or lean solid state amps. So one may work well in your situation, but it won’t give you the transparency of newer tube gear.

So my advice is to have your SA 250 checked out, give it a little burn in time and then either go for the "classic" golden c-j tube sound with a PV-10 or get a newer tube preamp if you want a more transparent sound.

You need a preamp and a DAC. Using the headphone output is not ideal. 

I agree that the SA 250 should be checked out.