Tweaking preamp and amp combination

I've owned the 3A Sigs and the SP9 MKII (and MKIII).  Neither caused any distortion on my vinyl.   What did cause the distortion you describe was bad cartridge setup, especially zenith.  
The Electro Harmonix tubes were ho-hum IMO.  In the MKII I liked Telefunken ECC88 but in the more detailed MarkIII I liked the E88CC.  
The 3A Sigs were sensitive to cables for sure.  I had cheap Monster Powerline 2 and going to Acoustic Zen Satori reduced glare dramatically.  Also, reducing "midrange glare" is a function of the tweeter control, not the midrange control, so a heads up on that.  Good Luck!  

Thanks all for the recommendations.  I decided to take guidance to revisit my cartridge setup.  I found a more current document online and when thru the tonearm setup. I realigned the cartridge on my tonearm and reset tracking force. I then set VTA and azimuth.  These changes have corrected the issues I was facing with cymbals and high timbre vocals. 

I'm due for a tube replacement in early July on the pre-amp so next step will be to try a different brand of tubes.  Thanks again.   

Option One looks good, I did that years ago when I had the same amp.....it was not a subtle upgrade....everything that was good got better. Let us know what you decided.