Will a high quality preamp really make a difference in sound?? Also speaker cable

I think I would reframe the question.  Is a standalone preamp with lots of inputs necessary?  If you only listen only to digital then many DACs have well implemented preamps built into the unit (not in digital domaine).  If you listen to digital and vinyl as I do, some DACs have an extra analog input as does my MSB Reference. 

Preamp: duh.

Cables: The Cable Choir may have made a Religious Convert out of me!

The other day, I put in a different cable that was a foot longer to run from my phase aligners to my amps. Afterwards, something didn’t sound right. I switched back. Better!

I have no idea what the brands are. The longer one was sheathed in a synthetic fabric. The other, in rubber.

If a preamp is really all upside and no downside, as contended here by some, then the truly high end systems should have a couple of preamps daisy chained to get the best possible sound.  Odd that you never see that, even when funding is no issue.

Any time a signal is processed / amplified it is changed, unless you assume the amplifier is absolutely perfect.  Of course that is never the case.

If you have a deficiency in you system, like you need to add some tube warmth, or tone controls are required to balance the sound, then a preamp is potentially in order.  But note that the effect of the preamp is to alter the sound to achieve some end. 

I am not suggesting that there is no place for a preamp, but useful to be aware of what it is doing, both good and bad.

I would say that the preamp definitely matters, and I am in the "cables do matter" camp.  I started with an MSB Discrete DAC and volume control.  My dealer lent me an ARC LS28SE to try.  I found it to be no different or extremely minimally better.  Then I put in an ARC REF 6 with a Shunyata Sigma power cord. Big difference in SQ, IMHO.  Then I replaced my Morrow Audio SP-7 speaker wire with Shunyata Sigma's.  Again, a very noticeable improvement.  Not night and day of course, but a definite audible improvement.  So yes, based on my own experience, a good preamp can definitely make a good difference, and so can good speaker cables.